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Info file: termcap,    -*-Text-*-
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from file: termcap.texinfo

This file documents the termcap library of the GNU system.

Copyright (C) 1988 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by the Foundation.

File: termcap  Node: Top, Prev: (DIR), Up: (DIR), Next: Introduction

* Menu:

* Introduction::What is termcap?  Why this manual?
* Library::     The termcap library functions.
* Data Base::   What terminal descriptions in `/etc/termcap' look like.
* Capabilities::Definitions of the individual terminal capabilities:
                 how to write them in descriptions, and how to use
                 their values to do display updating.
* Var Index::   Index of C functions and variables.
* Cap Index::   Index of termcap capabilities.
* Index::       Concept index.


File: termcap  Node: Introduction, Prev: Top, Up: Top, Next: Library

Introduction
************

"Termcap" is a library and data base that enables programs to use
display terminals in a terminal-independent manner.  It originated in
Berkeley Unix.

The termcap data base describes the capabilities of hundreds of different
display terminals in great detail.  Some examples of the information
recorded for a terminal could include how many columns wide it is, what
string to send to move the cursor to an arbitrary position (including how
to encode the row and column numbers), how to scroll the screen up one or
several lines, and how much padding is needed for such a scrolling
operation.

The termcap library is provided for easy access this data base in programs
that want to do terminal-independent character-based display output.

This manual describes the GNU version of the termcap library, which has
some extensions over the Unix version.  All the extensions are identified
as such, so this manual also tells you how to use the Unix termcap.

The GNU version of the termcap library is available free as source code,
for use in free programs, and runs on Unix and VMS systems (at least).  You
can find it in the GNU Emacs distribution in the files `termcap.c' and
`tparam.c'.

This manual was written for the GNU project, whose goal is to develop a
complete free operating system upward-compatible with Unix for user
programs.  The project is approximately two thirds complete.  For more
information on the GNU project, including the GNU Emacs editor and the
mostly-portable optimizing C compiler, send one dollar to

     Free Software Foundation
     675 Mass Ave
     Cambridge, MA 02139


File: termcap  Node: Library, Prev: Top, Up: Top, Next: Data Base

The Termcap Library
*******************

The termcap library is the application programmer's interface to the
termcap data base.  It contains functions for the following purposes:

   * Finding the description of the user's terminal type (`tgetent').

   * Interrogating the description for information on various topics
     (`tgetnum', `tgetflag', `tgetstr').

   * Computing and performing padding (`tputs').

   * Encoding numeric parameters such as cursor positions into the
     terminal-specific form required for display commands (`tparam',
     `tgoto').

* Menu:

* Preparation:: Preparing to use the termcap library.
* Find::        Finding the description of the terminal being used.
* Interrogate:: Interrogating the description for particular capabilities.
* Initialize::  Initialization for output using termcap.
* Padding::     Outputting padding.
* Parameters::  Encoding parameters such as cursor positions.


File: termcap  Node: Preparation, Prev: Library, Up: Library, Next: Find

Preparing to Use the Termcap Library
====================================

To use the termcap library in a program, you need two kinds of preparation:

   * The compiler needs declarations of the functions and variables in the
     library.

     On GNU systems, it suffices to include the header file `termcap.h'
     in each source file that uses these functions and variables.

     On Unix systems, there is often no such header file.  Then you must
     explictly declare the variables as external.  You can do likewise for
     the functions, or let them be implicitly declared and cast their
     values from type `int' to the appropriate type.

     We illustrate the declarations of the individual termcap library
     functions with ANSI C prototypes because they show how to pass the
     arguments.  If you are not using the GNU C compiler, you probably
     cannot use function prototypes, so omit the argument types and names
     from your declarations.

   * The linker needs to search the library.  Usually either `-ltermcap'
     or `-ltermlib' as an argument when linking will do this.


File: termcap  Node: Find, Prev: Preparation, Up: Library, Next: Interrogate

Finding a Terminal Description: `tgetent'
=========================================

An application program that is going to use termcap must first look up the
description of the terminal type in use.  This is done by calling
`tgetent', whose declaration in ANSI Standard C looks like:

     int tgetent (char *BUFFER, char *TERMTYPE);

This function finds the description and remembers it internally so that
you can interrogate it about specific terminal capabilities
(*Note Interrogate::).

The argument TERMTYPE is a string which is the name for the type of
terminal to look up.  Usually you would obtain this from the environment
variable `TERM' using `getenv ("TERM")'.

If you are using the GNU version of termcap, you can alternatively ask
`tgetent' to allocate enough space.  Pass a null pointer for BUFFER, and
`tgetent' itself allocates the storage using `malloc'.  In this case the
returned value on success is the address of the storage, cast to `int'.
But normally there is no need for you to look at the address.  Do not
free the storage yourself.

With the Unix version of termcap, you must allocate space for the
description yourself and pass the address of the space as the argument
BUFFER.  There is no way you can tell how much space is needed, so
the convention is to allocate a buffer 2048 characters long and assume that
is enough.  (Formerly the convention was to allocate 1024 characters and
assume that was enough.  But one day, for one kind of terminal, that was
not enough.)

No matter how the space to store the description has been obtained,
termcap records its address internally for use when you later
interrogate the description with `tgetnum', `tgetstr' or `tgetflag'.  If
the buffer was allocated by termcap, it will be freed by termcap too if
you call `tgetent' again.  If the buffer was provided by you, you must
make sure that its contents remain unchanged for as long as you still
plan to interrogate the description.

The return value of `tgetent' is -1 if there is some difficulty
accessing the data base of terminal types, 0 if the data base is accessible
but the specified type is not defined in it, and some other value
otherwise.

Here is how you might use the function `tgetent':

     #ifdef unix
     static char term_buffer[2048];
     #else
     #define term_buffer 0
     #endif

     init_terminal_data ()
     {
       char *termtype = getenv ("TERM");
       int success;

       if (termtype == 0)
         fatal ("Specify a terminal type with `setenv TERM <yourtype>'.\n");

       success = tgetent (term_buffer, termtype);
       if (success < 0)
         fatal ("Could not access the termcap data base.\n");
       if (success == 0)
         fatal ("Terminal type `%s' is not defined.\n", termtype);
     }

Here we assume the function `fatal' prints an error message and exits.

If the environment variable `TERMCAP' is defined, its value is used to
override the terminal type data base.  The function `tgetent' checks the
value of `TERMCAP' automatically.  If the value starts with `/' then it
is taken as a file name to use as the data base file, instead of
`/etc/termcap' which is the standard data base.  If the value does not
start with `/' then it is itself used as the terminal description,
provided that the terminal type TERMTYPE is among the types it claims to
apply to.  *Note Data Base::, for information on the format of a
terminal description.


File: termcap  Node: Interrogate, Prev: Find, Up: Library, Next: Initialize

Interrogating the Terminal Description
======================================

Each piece of information recorded in a terminal description is called a
"capability".  Each defined terminal capability has a two-letter code
name and a specific meaning.  For example, the number of columns is named
`co'.  *Note Capabilities::, for definitions of all the standard
capability names.

Once you have found the proper terminal description with `tgetent'
(*Note Find::), your application program must "interrogate" it for
various terminal capabilities.  You must specify the two-letter code of
the capability whose value you seek.

Capability values can be numeric, boolean (capability is either present
or absent) or strings.  Any particular capability always has the same
value type; for example, `co' always has a numeric value, while `am'
(automatic wrap at margin) is always a flag, and `cm' (cursor motion
command) always has a string value.  The documentation of each
capability says which type of value it has.

There are three functions to use to get the value of a capability,
depending on the type of value the capability has.  Here are their
declarations in ANSI C:

     int tgetnum (char *NAME);
     int tgetflag (char *NAME);
     char *tgetstr (char *NAME, char **AREA);

`tgetnum'
     Use `tgetnum' to get a capability value that is numeric.  The
     argument NAME is the two-letter code name of the capability.  If
     the capability is present, `tgetnum' returns the numeric value
     (which is nonnegative).  If the capability is not mentioned in the
     terminal description, `tgetnum' returns -1.

`tgetflag'
     Use `tgetflag' to get a boolean value.  If the capability
     NAME is present in the terminal description, `tgetflag'
     returns 1; otherwise, it returns 0.

`tgetstr'
     Use `tgetstr' to get a string value.  It returns a pointer to a
     string which is the capability value, or a null pointer if the
     capability is not present in the terminal description.

     There are two ways `tgetstr' can find space to store the string value:

        * You can ask `tgetstr' to allocate the space.  Pass a null
          pointer for the argument AREA, and `tgetstr' will use
          `malloc' to allocate storage big enough for the value.
          Termcap will never free this storage or refer to it again; you
          should free it when you are finished with it.

          This method is more robust, since there is no need to guess how
          much space is needed.  But it is supported only by the GNU
          termcap library.

        * You can provide the space.  Provide for the argument AREA the
          address of a pointer variable of type `char *'.  Before calling
          `tgetstr', initialize the variable to point at available space.
          Then `tgetstr' will store the string value in that space and will
          increment the pointer variable to point after the space that has been
          used.  You can use the same pointer variable for many calls to
          `tgetstr'.

          There is no way to determine how much space is needed for a single
          string, and no way for you to prevent or handle overflow of the area
          you have provided.  However, you can be sure that the total size of
          all the string values you will obtain from the terminal description is
          no greater than the size of the description (unless you get the same
          capability twice).  You can determine that size with `strlen' on
          the buffer you provided to `tgetent'.  See below for an example.

          Providing the space yourself is the only method supported by the Unix
          version of termcap.

Note that you do not have to specify a terminal type or terminal
description for the interrogation functions.  They automatically use the
description found by the most recent call to `tgetent'.

Here is an example of interrogating a terminal description for various
capabilities, with conditionals to select between the Unix and GNU methods
of providing buffer space.

     char *tgetstr ();

     char *cl_string, *cm_string;
     int height;
     int width;
     int auto_wrap;

     char PC;   /* For tputs.  */
     char *BC;  /* For tgoto.  */
     char *UP;

     interrogate_terminal ()
     {
     #ifdef UNIX
       /* Here we assume that an explicit term_buffer
          was provided to tgetent.  */
       char *buffer
         = (char *) malloc (strlen (term_buffer));
     #define BUFFADDR &buffer
     #else
     #define BUFFADDR 0
     #endif

       char *temp;

       /* Extract information we will use.  */
       cl_string = tgetstr ("cl", BUFFADDR);
       cm_string = tgetstr ("cm", BUFFADDR);
       auto_wrap = tgetflag ("am");
       height = tgetnum ("li");
       width = tgetnum ("co");

       /* Extract information that termcap functions use.  */
       temp = tgetstr ("pc", BUFFADDR);
       PC = temp ? *temp : 0;
       BC = tgetstr ("le", BUFFADDR);
       UP = tgetstr ("up", BUFFADDR);
     }

*Note Padding::, for information on the variable `PC'.  *Note Using Parameters::, for information on `UP' and `BC'.


File: termcap  Node: Initialize, Prev: Interrogate, Up: Library, Next: Padding

Initialization for Use of Termcap
=================================

Before starting to output commands to a terminal using termcap,
an application program should do two things:

   * Initialize various global variables which termcap library output
     functions refer to.  These include `PC' and `ospeed' for padding
     (*Note Output Padding::) and `UP' and `BC' for cursor motion (*Note
     tgoto::).

   * Tell the kernel to turn off alteration and padding of horizontal-tab
     characters sent to the terminal.

To turn off output processing in Berkeley Unix you would use `ioctl'
with code `TIOCLSET' to set the bit named `LLITOUT', and clear the bits
`ANYDELAY' using `TIOCSETN'.  In POSIX or System V, you must clear the
bit named `OPOST'.  Refer to the system documentation for details.

If you do not set the terminal flags properly, some older terminals will
not work.  This is because their commands may contain the characters that
normally signify newline, carriage return and horizontal tab---characters
which the kernel thinks it ought to modify before output.

When you change the kernel's terminal flags, you must arrange to restore
them to their normal state when your program exits.  This implies that the
program must catch fatal signals such as `SIGQUIT' and `SIGINT'
and restore the old terminal flags before actually terminating.

Modern terminals' commands do not use these special characters, so if you
do not care about problems with old terminals, you can leave the kernel's
terminal flags unaltered.


File: termcap  Node: Padding, Prev: Initialize, Up: Library, Next: Parameters

Padding
=======

"Padding" means outputting null characters following a terminal display
command that takes a long time to execute.  The terminal description says
which commands require padding and how much; the function `tputs',
described below, outputs a terminal command while extracting from it the
padding information, and then outputs the padding that is necessary.

* Menu:

* Why Pad::          Explanation of padding.
* Describe Padding:: The data base says how much padding a terminal needs.
* Output Padding::   Using `tputs' to output the needed padding.


File: termcap  Node: Why Pad, Prev: Padding, Up: Padding, Next: Describe Padding

Why Pad, and How
----------------

Most types of terminal have commands that take longer to execute than they
do to send over a high-speed line.  For example, clearing the screen may
take 20msec once the entire command is received.  During that time, on a
9600 bps line, the terminal could receive about 20 additional output
characters while still busy clearing the screen.  Every terminal has a
certain amount of buffering capacity to remember output characters that
cannot be processed yet, but too many slow commands in a row can cause the
buffer to fill up.  Then any additional output that cannot be processed
immediately will be lost.

To avoid this problem, we normally follow each display command with enough
useless charaters (usually null characters) to fill up the time that the
display command needs to execute.  This does the job if the terminal throws
away null characters without using up space in the buffer (which most
terminals do).  If enough padding is used, no output can ever be lost.  The
right amount of padding avoids loss of output without slowing down
operation, since the time used to transmit padding is time that nothing
else could be done.

The number of padding characters needed for an operation depends on the
line speed.  In fact, it is proportional to the line speed.  A 9600 baud
line transmits about one character per msec, so the clear screen command in
the example above would need about 20 characters of padding.  At 1200 baud,
however, only about 3 characters of padding are needed to fill up 20msec.


File: termcap  Node: Describe Padding, Prev: Why Pad, Up: Padding, Next: Output Padding

Specifying Padding in a Terminal Description
--------------------------------------------

In the terminal description, the amount of padding required by each display
command is recorded as a sequence of digits at the front of the command.
These digits specify the padding time in msec.  They can be followed
optionally by a decimal point and one more digit, which is a number of
tenths of msec.

Sometimes the padding needed by a command depends on the cursor position.
For example, the time taken by an "insert line" command is usually
proportional to the number of lines that need to be moved down or cleared.
An asterisk (`*') following the padding time says that the time
should be multiplied by the number of screen lines affected by the command.

     :al=1.3*\E[L:

is used to describe the "insert line" command for a certain terminal.
The padding required is 1.3 msec per line affected.  The command itself is
`ESC [ L'.

The padding time specified in this way tells `tputs' how many pad
characters to output.  *Note Output Padding::.

Two special capability values affect padding for all commands.  These are
the `pc' and `pb'.  The variable `pc' specifies the
character to pad with, and `pb' the speed below which no padding is
needed.  The defaults for these variables, a null character and 0,
are correct for most terminals.  *Note Pad Specs::.


File: termcap  Node: Output Padding, Prev: Describe Padding, Up: Padding

Performing Padding with `tputs'
-------------------------------

Use the termcap function `tputs' to output a string containing an
optional padding spec of the form described above (*Note Describe Padding::).  The function `tputs' strips off and decodes the padding
spec, outputs the rest of the string, and then outputs the appropriate
padding.  Here is its declaration in ANSI C:

     char PC;
     short ospeed;

     int tputs (char *STRING, int NLINES, int (*OUTFUN) ());

Here STRING is the string (including padding spec) to be output;
NLINES is the number of lines affected by the operation, which is
used to multiply the amount of padding if the padding spec ends with a
`*'.  Finally, OUTFUN is a function (such as `fputchar')
that is called to output each character.  When actually called,
OUTFUN should expect one argument, a character.

The operation of `tputs' is controlled by two global variables,
`ospeed' and `PC'.  The value of `ospeed' is supposed to be
the terminal output speed, encoded as in the `ioctl' system call which
gets the speed information.  This is needed to compute the number of
padding characters.  The value of `PC' is the character used for
padding.

You are responsible for storing suitable values into these variables
before using `tputs'.  The value stored into the `PC' variable should be
taken from the `pc' capability in the terminal description (*Note Pad
Specs::).  Store zero in `PC' if there is no `pc' capability.

The argument NLINES requires some thought.  Normally, it should be the
number of lines whose contents will be cleared or moved by the command.
For cursor motion commands, or commands that do editing within one line,
use the value 1.  For most commands that affect multiple lines, such as
`al' (insert a line) and `cd' (clear from the cursor to the end of the
screen), NLINES should be the screen height minus the current vertical
position (origin 0).  For multiple insert and scroll commands such as
`AL' (insert multiple lines), that same value for NLINES is correct; the
number of lines being inserted is not correct.

If a "scroll window" feature is used to reduce the number of lines
affected by a command, the value of NLINES should take this into
account.  This is because the delay time required depends on how much work
the terminal has to do, and the scroll window feature reduces the work.
*Note Scrolling::.

Commands such as `ic' and `dc' (insert or delete characters) are
problematical because the padding needed by these commands is proportional
to the number of characters affected, which is the number of columns from
the cursor to the end of the line.  It would be nice to have a way to
specify such a dependence, and there is no need for dependence on vertical
position in these commands, so it is an obvious idea to say that for these
commands NLINES should really be the number of columns affected.
However, the definition of termcap clearly says that NLINES is always
the number of lines affected, even in this case, where it is always 1.  It
is not easy to change this rule now, because too many programs and terminal
descriptions have been written to follow it.

Because NLINES is always 1 for the `ic' and `dc' strings,
there is no reason for them to use `*', but some of them do.  These
should be corrected by deleting the `*'.  If, some day, such entries
have disappeared, it may be possible to change to a more useful convention
for the NLINES argument for these operations without breaking any
programs.


File: termcap  Node: Parameters, Prev: Padding, Up: Library

Filling In Parameters
=====================

Some terminal control strings require numeric "parameters".  For
example, when you move the cursor, you need to say what horizontal and
vertical positions to move it to.  The value of the terminal's `cm'
capability, which says how to move the cursor, cannot simply be a string of
characters; it must say how to express the cursor position numbers and
where to put them within the command.

The specifications of termcap include conventions as to which string-valued
capabilities require parameters, how many parameters, and what the
parameters mean; for example, it defines the `cm' string to take
two parameters, the vertical and horizontal positions, with 0,0 being the
upper left corner.  These conventions are described where the individual
commands are documented.

Termcap also defines a language used within the capability definition for
specifying how and where to encode the parameters for output.  This language
uses character sequences starting with `%'.  (This is the same idea as
`printf', but the details are different.)  The language for parameter
encoding is described in this section.

A program that is doing display output calls the functions `tparam' or
`tgoto' to encode parameters according to the specifications.  These
functions produce a string containing the actual commands to be output (as
well a padding spec which must be processed with `tputs';
*Note Padding::).

* Menu:

* Encode Parameters:: The language for encoding parameters.
* Using Parameters::  Outputting a string command with parameters.


File: termcap  Node: Encode Parameters, Prev: Parameters, Up: Parameters, Next: Using Parameters

Describing the Encoding
-----------------------

A terminal command string that requires parameters contains special
character sequences starting with `%' to say how to encode the
parameters.  These sequences control the actions of `tparam' and
`tgoto'.

The parameters values passed to `tparam' or `tgoto' are
considered to form a vector.  A pointer into this vector determines
the next parameter to be processed.  Some of the `%'-sequences
encode one parameter and advance the pointer to the next parameter.
Other `%'-sequences alter the pointer or alter the parameter
values without generating output.

For example, the `cm' string for a standard ANSI terminal is written
as `\E[%i%d;%dH'.  (`\E' stands for ESC.)  `cm' by
convention always requires two parameters, the vertical and horizontal goal
positions, so this string specifies the encoding of two parameters.  Here
`%i' increments the two values supplied, and each `%d' encodes
one of the values in decimal.  If the cursor position values 20,58 are
encoded with this string, the result is `\E[21;59H'.

First, here are the `%'-sequences that generate output.  Except for
`%%', each of them encodes one parameter and advances the pointer
to the following parameter.

`%%'
     Output a single `%'.  This is the only way to represent a literal
     `%' in a terminal command with parameters.  `%%' does not
     use up a parameter.

`%d'
     As in `printf', output the next parameter in decimal.

`%2'
     Like `%02d' in `printf': output the next parameter in
     decimal, and always use at least two digits.

`%3'
     Like `%03d' in `printf': output the next parameter in
     decimal, and always use at least three digits.  Note that `%4'
     and so on are *not* defined.

`%.'
     Output the next parameter as a single character whose ASCII code is
     the parameter value.  Like `%c' in `printf'.

`%+CHAR'
     Add the next parameter to the character CHAR, and output the
     resulting character.  For example, `%+ ' represents 0 as a space,
     1 as `!', etc.

The following `%'-sequences specify alteration of the parameters (their
values, or their order) rather than encoding a parameter for output.
They generate no output; they are used only for their side effects on
the parameters.  Also, they do not advance the "next parameter" pointer
except as explicitly stated.  Only `%i', `%r' and `%>' are defined in
standard Unix termcap.  The others are GNU extensions.

`%i'
     Increment the next two parameters.  This is used for terminals that
     expect cursor positions in origin 1.  For example, `%i%d,%d' would
     output two parameters with `1' for 0, `2' for 1, etc.

`%r'
     Interchange the next two parameters.  This is used for terminals whose
     cursor positioning command expects the horizontal position first.

`%s'
     Skip the next parameter.  Do not output anything.

`%b'
     Back up one parameter.  The last parameter used will become once again
     the next parameter to be output, and the next output command will use
     it.  Using `%b' more than once, you can back up any number of
     parameters, and you can refer to each parameter any number of times.

`%>C1C2'
     Conditionally increment the next parameter.  Here C1 and C2 are
     characters which stand for their ASCII codes as numbers.  If the
     next parameter is greater than the ASCII code of C1, the ASCII code
     of C2 is added to it.

`%a OP TYPE POS'
     Perform arithmetic on the next parameter, do not use it up, and do not
     output anything.  Here OP specifies the arithmetic operation,
     while TYPE and POS together specify the other operand.

     Spaces are used above to separate the operands for clarity; the spaces
     don't appear in the data base, where this sequence is exactly five
     characters long.

     The character OP says what kind of arithmetic operation to
     perform.  It can be any of these characters:

     `='
          assign a value to the next parameter, ignoring its old value.
          The new value comes from the other operand.

     `+'
          add the other operand to the next parameter.

     `-'
          subtract the other operand from the next parameter.

     `*'
          multiply the next parameter by the other operand.

     `/'
          divide the next parameter by the other operand.

     The "other operand" may be another parameter's value or a constant;
     the character TYPE says which.  It can be:

     `p'
          Use another parameter.  The character POS says which
          parameter to use.  Subtract 64 from its ASCII code to get the
          position of the desired parameter relative to this one.  Thus,
          the character `A' as POS means the parameter after the
          next one; the character `?' means the parameter before the
          next one.

     `c'
          Use a constant value.  The character POS specifies the
          value of the constant.  The 0200 bit is cleared out, so that 0200
          can be used to represent zero.

The following `%'-sequences are special purpose hacks to compensate
for the weird designs of obscure terminals.  They modify the next parameter
or the next two parameters but do not generate output and do not use up any
parameters.  `%m' is a GNU extension; the others are defined in
standard Unix termcap.

`%n'
     Exclusive-or the next parameter with 0140, and likewise the parameter
     after next.

`%m'
     Complement all the bits of the next parameter and the parameter after next.

`%B'
     Encode the next parameter in BCD.  It alters the value of the
     parameter by adding six times the quotient of the parameter by ten.
     Here is a C statement that shows how the new value is computed:

          PARM = (PARM / 10) * 16 + PARM % 10;

`%D'
     Transform the next parameter as needed by Delta Data terminals.
     This involves subtracting twice the remainder of the parameter by 16.

          PARM -= 2 * (PARM % 16);


File: termcap  Node: Using Parameters, Prev: Encode Parameters, Up: Parameters

Sending Display Commands with Parameters
----------------------------------------

The termcap library functions `tparam' and `tgoto' serve as the
analog of `printf' for terminal string parameters.  The newer function
`tparam' is a GNU extension, more general but missing from Unix
termcap.  The original parameter-encoding function is `tgoto', which
is preferable for cursor motion.

* Menu:

* tparam::   The general case, for GNU termcap only.
* tgoto::    The special case of cursor motion.


File: termcap  Node: tparam, Prev: Using Parameters, Up: Using Parameters, Next: tgoto

`tparam'
........

The function `tparam' can encode display commands with any number of
parameters and allows you to specify the buffer space.  It is the preferred
function for encoding parameters for all but the `cm' capability.  Its
ANSI C declaration is as follows:

     char *tparam (char *CTLSTRING, char *BUFFER, int SIZE, int PARM1,...)

The arguments are a control string CTLSTRING (the value of a terminal
capability, presumably), an output buffer BUFFER and SIZE, and
any number of integer parameters to be encoded.  The effect of
`tparam' is to copy the control string into the buffer, encoding
parameters according to the `%' sequences in the control string.

You describe the output buffer by its address, BUFFER, and its size
in bytes, SIZE.  If the buffer is not big enough for the data to be
stored in it, `tparam' calls `malloc' to get a larger buffer.  In
either case, `tparam' returns the address of the buffer it ultimately
uses.  If the value equals BUFFER, your original buffer was used.
Otherwise, a new buffer was allocated, and you must free it after you are
done with printing the results.  If you pass zero for SIZE and
BUFFER, `tparam' always allocates the space with `malloc'.

All capabilities that require parameters also have the ability to specify
padding, so you should use `tputs' to output the string produced by
`tparam'.  *Note Padding::.  Here is an example.

     {
       char *buf;
       char buffer[40];

       buf = tparam (command, buffer, 40, parm);
       tputs (buf, 1, fputchar);
       if (buf != buffer)
         free (buf);
     }

If a parameter whose value is zero is encoded with `%.'-style encoding,
the result is a null character, which will confuse `tputs'.  This would
be a serious problem, but luckily `%.' encoding is used only by a few
old models of terminal, and only for the `cm' capability.  To solve the
problem, use `tgoto' rather than `tparam' to encode the `cm' capability.


File: termcap  Node: tgoto, Prev: tparam, Up: Using Parameters

`tgoto'
.......

The special case of cursor motion is handled by `tgoto'.  There
are two reasons why you might choose to use `tgoto':

   * For Unix compatibility, because Unix termcap does not have `tparam'.

   * For the `cm' capability, since `tgoto' has a special feature
     to avoid problems with null characters, tabs and newlines on certain old
     terminal types that use `%.' encoding for that capability.

Here is how `tgoto' might be declared in ANSI C:

     char *tgoto (char *CSTRING, int HPOS, int VPOS)

There are three arguments, the terminal description's `cm' string and
the two cursor position numbers; `tgoto' computes the parametrized
string in an internal static buffer and returns the address of that buffer.
The next time you use `tgoto' the same buffer will be reused.

Parameters encoded with `%.' encoding can generate null characters,
tabs or newlines.  These might cause trouble: the null character because
`tputs' would think that was the end of the string, the tab because
the kernel or other software might expand it into spaces, and the newline
becaue the kernel might add a carriage-return, or padding characters
normally used for a newline.  To prevent such problems, `tgoto' is
careful to avoid these characters.  Here is how this works: if the target
cursor position value is such as to cause a problem (that is to say, zero,
nine or ten), `tgoto' increments it by one, then compensates by
appending a string to move the cursor back or up one position.

The compensation strings to use for moving back or up are found in global
variables named `BC' and `UP'.  These are actual external C
variables with upper case names; they are declared `char *'.  It is up
to you to store suitable values in them, normally obtained from the
`le' and `up' terminal capabilities in the terminal description
with `tgetstr'.  Alternatively, if these two variables are both zero,
the feature of avoiding nulls, tabs and newlines is turned off.

It is safe to use `tgoto' for commands other than `cm' only if
you have stored zero in `BC' and `UP'.

Note that `tgoto' reverses the order of its operands: the horizontal
position comes before the vertical position in the arguments to `tgoto',
even though the vertical position comes before the horizontal in the
parameters of the `cm' string.  If you use `tgoto' with a command such
as `AL' that takes one parameter, you must pass the parameter to `tgoto'
as the "vertical position".


File: termcap  Node: Data Base, Prev: Library, Up: Top, Next: Capabilities

The Format of the Data Base
***************************

The termcap data base of terminal descriptions is stored in the file
`/etc/termcap'.  It contains terminal descriptions, blank lines, and
comments.

A terminal description starts with one or more names for the terminal type.
The information in the description is a series of "capability names"
and values.  The capability names have standard meanings
(*Note Capabilities::) and their values describe the terminal.

* Menu:

* Format::            Overall format of a terminal description.
* Capability Format:: Format of capabilities within a description.
* Naming::            Naming conventions for terminal types.
* Inheriting::        Inheriting part of a description from
                        a related terminal type.


File: termcap  Node: Format, Prev: Data Base, Up: Data Base, Next: Capability Format

Terminal Description Format
===========================

Aside from comments (lines starting with `#', which are ignored), each
nonblank line in the termcap data base is a terminal description.
A terminal description is nominally a single line, but it can be split
into multiple lines by inserting the two characters `\ newline'.
This sequence is ignored wherever it appears in a description.

The preferred way to split the description is between capabilities: insert
the four characters `: \ newline tab' immediately before any colon.
This allows each sub-line to start with some indentation.  This works
because, after the `\ newline' are ignored, the result is `: tab
:'; the first colon ends the preceding capability and the second colon
starts the next capability.  If you split with `\ newline' alone, you
may not add any indentation after them.

Here is a real example of a terminal description:

     dw|vt52|DEC vt52:\
             :cr=^M:do=^J:nl=^J:bl=^G:\
             :le=^H:bs:cd=\EJ:ce=\EK:cl=\EH\EJ:cm=\EY%+ %+ :co#80:li#24:\
             :nd=\EC:ta=^I:pt:sr=\EI:up=\EA:\
             :ku=\EA:kd=\EB:kr=\EC:kl=\ED:kb=^H:

Each terminal description begins with several names for the terminal type.
The names are separated by `|' characters, and a colon ends the last
name.  The first name should be two characters long; it exists only for the
sake of very old Unix systems and is never used in modern systems.  The
last name should be a fully verbose name such as "DEC vt52" or "Ann
Arbor Ambassador with 48 lines".  The other names should include whatever
the user ought to be able to specify to get this terminal type, such as
`vt52' or `aaa-48'.  *Note Naming::, for information on how to
choose terminal type names.

After the terminal type names come the terminal capabilities, separated by
colons and with a colon after the last one.  Each capability has a
two-letter name, such as `cm' for "cursor motion string" or `li'
for "number of display lines".


File: termcap  Node: Capability Format, Prev: Format, Up: Data Base, Next: Naming

Writing the Capabilities
========================

There are three kinds of capabilities: flags, numbers, and strings.  Each
kind has its own way of being written in the description.  Each defined
capability has by convention a particular kind of value; for example,
`li' always has a numeric value and `cm' always a string value.

A flag capability is thought of as having a boolean value: the value is
true if the capability is present, false if not.  When the capability is
present, just write its name between two colons.

A numeric capability has a value which is a nonnegative number.  Write
the capability name, a `#', and the number, between two colons.  For
example, `...:li#48:...' is how you specify the `li' capability for 48
lines.

A string-valued capability has a value which is a sequence of
characters.  Usually these are the characters used to perform some
display operation.  Write the capability name, a `=', and the characters
of the value, between two colons.  For example, `...:cm=\E[%i%d;%dH:...'
is how the cursor motion command for a standard ANSI terminal would be
specified.

Special characters in the string value can be expressed using `\'-escape
sequences as in C; in addition, `\E' stands for ESC.  `^' is also a kind
of escape character; `^' followed by CHAR stands for the
control-equivalent of CHAR.  Thus, `^a' stands for the character
control-a, just like `\001'.  `\' and `^' themselves can be represented
as `\\' and `\^'.

To include a colon in the string, you must write `\072'.  You might
ask, "Why can't `\:' be used to represent a colon?"  The reason is
that the interrogation functions do not count slashes while looking for a
capability.  Even if `:ce=ab\:cd:' were interpreted as giving the
`ce' capability the value `ab:cd', it would also appear to define
`cd' as a flag.

The string value will often contain digits at the front to specify padding
(*Note Padding::) and/or `%'-sequences within to specify how to encode
parameters (*Note Parameters::).  Although these things are not to be
output literally to the terminal, they are considered part of the value of
the capability.  They are special only when the string value is processed
by `tputs', `tparam' or `tgoto'.  By contrast, `\' and
`^' are considered part of the syntax for specifying the characters
in the string.

Let's look at the VT52 example again:

     dw|vt52|DEC vt52:\
             :cr=^M:do=^J:nl=^J:bl=^G:\
             :le=^H:bs:cd=\EJ:ce=\EK:cl=\EH\EJ:cm=\EY%+ %+ :co#80:li#24:\
             :nd=\EC:ta=^I:pt:sr=\EI:up=\EA:\
             :ku=\EA:kd=\EB:kr=\EC:kl=\ED:kb=^H:

Here we see the numeric-valued capabilities `co' and `li', the
flags `bs' and `pt', and many string-valued capabilities.  Most
of the strings start with ESC represented as `\E'.  The rest
contain control characters represented using `^'.  The meanings of the
individual capabilities are defined elsewhere (*Note Capabilities::).


File: termcap  Node: Naming, Prev: Capability Format, Up: Data Base, Next: Inheriting

Terminal Type Name Conventions
==============================

There are conventions for choosing names of terminal types.  For one thing,
all letters should be in lower case.  The terminal type for a terminal in
its most usual or most fundamental mode of operation should not have a
hyphen in it.

If the same terminal has other modes of operation which require
different terminal descriptions, these variant descriptions are given
names made by adding suffixes with hyphens.  Such alternate descriptions
are used for two reasons:

   * When the terminal has a switch that changes its behavior.  Since the
     computer cannot tell how the switch is set, the user must tell the
     computer by choosing the appropriate terminal type name.

     For example, the VT-100 has a setup flag that controls whether the
     cursor wraps at the right margin.  If this flag is set to "wrap",
     you must use the terminal type `vt100-am'.  Otherwise you must use
     `vt100-nam'.  Plain `vt100' is defined as a synonym for either
     `vt100-am' or `vt100-nam' depending on the preferences of the local
     site.

     The standard suffix `-am' stands for "automatic margins".

   * To give the user a choice in how to use the terminal.  This is done
     when the terminal has a switch that the computer normally controls.

     For example, the Ann Arbor Ambassador can be configured with many
     screen sizes ranging from 20 to 60 lines.  Fewer lines make bigger
     characters but more lines let you see more of what you are editing.
     As a result, users have different preferences.  Therefore, termcap
     provides terminal types for many screen sizes.  If you choose type
     `aaa-30', the terminal will be configured to use 30 lines; if you
     choose `aaa-48', 48 lines will be used, and so on.

Here is a list of standard suffixes and their conventional meanings:

`-w'
     Short for "wide".  This is a mode that gives the terminal more
     columns than usual.  This is normally a user option.

`-am'
     "Automatic margins".  This is an alternate description for use when
     the terminal's margin-wrap switch is on; it contains the `am'
     flag.  The implication is that normally the switch is off and the
     usual description for the terminal says that the switch is off.

`-nam'
     "No automatic margins".  The opposite of `-am', this names an
     alternative description which lacks the `am' flag.  This implies
     that the terminal is normally operated with the margin-wrap switch
     turned on, and the normal description of the terminal says so.

`-na'
     "No arrows".  This terminal description initializes the terminal to
     keep its arrow keys in local mode.  This is a user option.

`-rv'
     "Reverse video".  This terminal description causes text output for
     normal video to appear as reverse, and text output for reverse
     video to come out as normal.  Often this description differs from
     the usual one by interchanging the two strings which turn reverse
     video on and off.

     This is a user option; you can choose either the "reverse video"
     variant terminal type or the normal terminal type, and termcap will
     obey.

`-s'
     "Status".  Says to enable use of a status line which ordinary output
     does not touch (*Note Status Line::).

     Some terminals have a special line that is used only as a status line.
     For these terminals, there is no need for an `-s' variant; the
     status line commands should be defined by default.  On other
     terminals, enabling a status line means removing one screen line from
     ordinary use and reducing the effective screen height.  For these
     terminals, the user can choose the `-s' variant type to request
     use of a status line.

`-NLINES'
     Says to operate with NLINES lines on the screen, for terminals
     such as the Ambassador which provide this as an option.  Normally this
     is a user option; by choosing the terminal type, you control how many
     lines termcap will use.

`-NPAGESp'
     Says that the terminal has NPAGES pages worth of screen memory,
     for terminals where this is a hardware option.

`-unk'
     Says that description is not for direct use, but only for reference in
     `tc' capabilities.  Such a description is a kind of subroutine,
     because it describes the common characteristics of several variant
     descriptions that would use other suffixes in place of `-unk'.


File: termcap  Node: Inheriting, Prev: Naming, Up: Data Base

Inheriting from Related Descriptions
====================================

When two terminal descriptions are similar, their identical parts do not
need to be given twice.  Instead, one of the two can be defined in terms of
the other, using the `tc' capability.  We say that one description
"refers to" the other, or "inherits from" the other.

The `tc' capability must be the last one in the terminal description,
and its value is a string which is the name of another terminal type which
is referred to.  For example,

     N9|aaa|ambassador|aaa-30|ann arbor ambassador/30 lines:\
             :ti=\E[2J\E[30;0;0;30p:\
             :te=\E[60;0;0;30p\E[30;1H\E[J:\
             :li#30:tc=aaa-unk:

defines the terminal type `aaa-30' (also known as plain `aaa') in
terms of `aaa-unk', which defines everything about the Ambassador that
is independent of screen height.  The types `aaa-36', `aaa-48'
and so on for other screen heights are likewise defined to inherit from
`aaa-unk'.

The capabilities overridden by `aaa-30' include `li', which says
how many lines there are, and `ti' and `te', which configure the
terminal to use that many lines.

The effective terminal description for type `aaa' consists of the text
shown above followed by the text of the description of `aaa-unk'.  The
`tc' capability is handled automatically by `tgetent', which
finds the description thus referenced and combines the two descriptions
(*Note Find::).  Therefore, only the implementor of the terminal
descriptions needs to think about using `tc'.  Users and application
programmers do not need to be concerned with it.

Since the reference terminal description is used last, capabilities
specified in the referring description override any specifications of the
same capabilities in the reference description.

The referring description can cancel out a capability without specifying
any new value for it by means of a special trick.  Write the capability in
the referring description, with the character `@' after the capability
name, as follows:

     NZ|aaa-30-nam|ann arbor ambassador/30 lines/no automatic-margins:\
             :am@:tc=aaa-30:


File: termcap  Node: Capabilities, Prev: Data Base, Up: Top, Next: Summary

Definitions of the Terminal Capabilities
****************************************

This section is divided into many subsections, each for one aspect of
use of display terminals.  For writing a display program, you usually need
only check the subsections for the operations you want to use.  For writing
a terminal description, you must read each subsection and fill in the
capabilities described there.

String capabilities that are display commands may require numeric
parameters (*Note Parameters::).  Most such capabilities do not use
parameters.  When a capability requires parameters, this is explicitly
stated at the beginning of its definition.  In simple cases, the first or
second sentence of the definition mentions all the parameters, in the order
they should be given, using a name
in upper case
for each one.  For example, the `rp' capability is a command that
requires two parameters; its definition begins as follows:

     String of commands to output a graphic character C, repeated N
     times.

In complex cases or when there are many parameters, they are described
explicitly.

When a capability is described as obsolete, this means that programs should
not be written to look for it, but terminal descriptions should still be
written to provide it.

When a capability is described as very obsolete, this means that it should
be omitted from terminal descriptions as well.

* Menu:

* Basic::             Basic characteristics.
* Screen Size::       Screen size, and what happens when it changes.
* Cursor Motion::     Various ways to move the cursor.
* Scrolling::         Pushing text up and down on the screen.
* Wrapping::          What happens if you write a character in the last column.
* Windows::           Limiting the part of the window that output affects.
* Clearing::          Erasing one or many lines.
* Insdel Line::       Making new blank lines in mid-screen; deleting lines.
* Insdel Char::       Inserting and deleting characters within a line.
* Standout::          Highlighting some of the text.
* Underlining::       Underlining some of the text.
* Cursor Visibility:: Making the cursor more or less easy to spot.
* Bell::              Attracts user's attention; not localized on the screen.
* Keypad::            Recognizing when function keys or arrows are typed.
* Meta Key::          META acts like an extra shift key.
* Initialization::    Commands used to initialize or reset the terminal.
* Pad Specs::         Info for the kernel on how much padding is needed.
* Status Line::       A status line displays "background" information.
* Half-Line::         Moving by half-lines, for superscripts and subscripts.
* Printer::           Controlling auxiliary printers of display terminals.


File: termcap  Node: Basic, Prev: Capabilities, Up: Capabilities, Next: Screen Size

Basic Characteristics
=====================

This section documents the capabilities that describe the basic and
nature of the terminal, and also those that are relevant to the output
of graphic characters.

`os'
     Flag whose presence means that the terminal can overstrike.  This
     means that outputting a graphic character does not erase whatever was
     present in the same character position before.  The terminals that can
     overstrike include printing terminals, storage tubes (all obsolete
     nowadays), and many bit-map displays.

`eo'
     Flag whose presence means that outputting a space can erase an
     overstrike.  If this is not present and overstriking is supported,
     output of a space has no effect except to move the cursor.

`gn'
     Flag whose presence means that this terminal type is a generic type
     which does not really describe any particular terminal.  Generic types
     are intended for use as the default type assigned when the user
     connects to the system, with the intention that the user should
     specify what type he really has.  One example of a generic type
     is the type `network'.

     Since the generic type cannot say how to do anything interesting with
     the terminal, termcap-using programs will always find that the
     terminal is too weak to be supported if the user has failed to specify
     a real terminal type in place of the generic one.  The `gn' flag
     directs these programs to use a different error message: "You have
     not specified your real terminal type", rather than "Your terminal
     is not powerful enough to be used".

`hc'
     Flag whose presence means this is a hardcopy terminal.

`rp'
     String of commands to output a graphic character C, repeated N
     times.  The first parameter value is the ASCII code for the desired
     character, and the second parameter is the number of times to repeat the
     character.  Often this command requires padding proportional to the
     number of times the character is repeated.  This effect can be had by
     using parameter arithmetic with `%'-sequences to compute the
     amount of padding, then generating the result as a number at the front
     of the string so that `tputs' will treat it as padding.

`hz'
     Flag whose presence means that the ASCII character `~' cannot be
     output on this terminal because it is used for display commands.

     Programs handle this flag by checking all text to be output and
     replacing each `~' with some other character(s).  If this is not
     done, the screen will be thoroughly garbled.

     The old Hazeltine terminals that required such treatment are probably
     very rare today, so you might as well not bother to support this flag.

`CC'
     String whose presence means the terminal has a settable command
     character.  The value of the string is the default command character
     (which is usually ESC).

     All the strings of commands in the terminal description should be
     written to use the default command character.  If you are writing an
     application program that changes the command character, use the
     `CC' capability to figure out how to translate all the display
     commands to work with the new command character.

     Most programs have no reason to look at the `CC' capability.

`xb'
     Flag whose presence identifies Superbee terminals which are unable to
     transmit the characters ESC and `Control-C'.  Programs which
     support this flag are supposed to check the input for the code sequences
     sent by the F1 and F2 keys, and pretend that ESC
     or `Control-C' (respectively) had been read.  But this flag is
     obsolete, and not worth supporting.


File: termcap  Node: Screen Size, Prev: Basic, Up: Capabilities, Next: Cursor Motion

Screen Size
===========

A terminal description has two capabilities, `co' and `li',
that describe the screen size in columns and lines.  But there is more
to the question of screen size than this.

On some operating systems the "screen" is really a window and the
effective width can vary.  On some of these systems, `tgetnum'
uses the actual width of the window to decide what value to return for
the `co' capability, overriding what is actually written in the
terminal description.  On other systems, it is up to the application
program to check the actual window width using a system call.  For
example, on BSD 4.3 systems, the system call `ioctl' with code
`TIOCGWINSZ' will tell you the current screen size.

On all window systems, termcap is powerless to advise the application
program if the user resizes the window.  Application programs must
deal with this possibility in a system-dependent fashion.  On some
systems the C shell handles part of the problem by detecting changes
in window size and setting the `TERMCAP' environment variable
appropriately.  This takes care of application programs that are
started subsequently.  It does not help application programs already
running.

On some systems, including BSD 4.3, all programs using a terminal get
a signal named `SIGWINCH' whenever the screen size changes.
Programs that use termcap should handle this signal by using
`ioctl TIOCGWINSZ' to learn the new screen size.

`co'
     Numeric value, the width of the screen in character positions.  Even
     hardcopy terminals normally have a `co' capability.

`li'
     Numeric value, the height of the screen in lines.


File: termcap  Node: Cursor Motion, Prev: Screen Size, Up: Capabilities, Next: Wrapping

Cursor Motion
=============

Termcap assumes that the terminal has a "cursor", a spot on the screen
where a visible mark is displayed, and that most display commands take
effect at the position of the cursor.  It follows that moving the cursor
to a specified location is very important.

There are many terminal capabilities for different cursor motion
operations.  A terminal description should define as many as possible, but
most programs do not need to use most of them.  One capability, `cm',
moves the cursor to an arbitrary place on the screen; this by itself is
sufficient for any application as long as there is no need to support
hardcopy terminals or certain old, weak displays that have only relative
motion commands.  Use of other cursor motion capabilities is an
optimization, enabling the program to output fewer characters in some
common cases.

If you plan to use the relative cursor motion commands in an application
program, you must know what the starting cursor position is.  To do this,
you must keep track of the cursor position and update the records each
time anything is output to the terminal, including graphic characters.
In addition, it is necessary to know whether the terminal wraps after
writing in the rightmost column.  *Note Wrapping::.

One other motion capability needs special mention: `nw' moves the
cursor to the beginning of the following line, perhaps clearing all the
starting line after the cursor, or perhaps not clearing at all.  This
capability is a least common denominator that is probably supported even by
terminals that cannot do most other things such as `cm' or `do'.
Even hardcopy terminals can support `nw'.

`cm'
     String of commands to position the cursor at line L, column C.
     Both parameters are origin-zero, and are defined relative to the
     screen, not relative to display memory.

     All display terminals except a few very obsolete ones support `cm',
     so it is acceptable for an application program to refuse to operate on
     terminals lacking `cm'.

`ho'
     String of commands to move the cursor to the upper left corner of the
     screen (this position is called the "home position").  In
     terminals where the upper left corner of the screen is not the same as
     the beginning of display memory, this command must go to the upper
     left corner of the screen, not the beginning of display memory.

     Every display terminal supports this capability, and many application
     programs refuse to operate if the `ho' capability is missing.

`ll'
     String of commands to move the cursor to the lower left corner of the
     screen.  On some terminals, moving up from home position does this,
     but programs should never assume that will work.  Just output the
     `ll' string (if it is provided); if moving to home position and
     then moving up is the best way to get there, the `ll' command
     will do that.

`cr'
     String of commands to move the cursor to the beginning of the line it
     is on.  If this capability is not specified, many programs assume
     they can use the ASCII carriage return character for this.

`le'
     String of commands to move the cursor left one column.  Unless the
     `bw' flag capability is specified, the effect is undefined if the
     cursor is at the left margin; do not use this command there.  If
     `bw' is present, this command may be used at the left margin, and
     it wraps the cursor to the last column of the preceding line.

`nd'
     String of commands to move the cursor right one column.  The effect is
     undefined if the cursor is at the right margin; do not use this
     command there, not even if `am' is present.

`up'
     String of commands to move the cursor vertically up one line.  The
     effect of sending this string when on the top line is undefined;
     programs should never use it that way.

`do'
     String of commands to move the cursor vertically down one line.  The
     effect of sending this string when on the bottom line is undefined;
     programs should never use it that way.

     The original idea was that this string would not contain a newline
     character and therefore could be used without disabling the kernel's usual
     habit of converting of newline into a carriage-return newline sequence.
     But many terminal descriptions do use newline in the `do' string, so
     this is not possible; a program which sends the `do' string must
     disable output conversion in the kernel (*Note Initialize::).

`bw'
     Flag whose presence says that `le' may be used in column zero
     to move to the last column of the preceding line.  If this flag
     is not present, `le' should not be used in column zero.

`nw'
     String of commands to move the cursor to start of next line, possibly
     clearing rest of line (following the cursor) before moving.

`DO', `UP', `LE', `RI'
     Strings of commands to move the cursor N lines down vertically,
     up vertically, or N columns left or right.  Do not attempt to
     move past any edge of the screen with these commands; the effect of
     trying that is undefined.  Only a few terminal descriptions provide
     these commands, and most programs do not use them.

`CM'
     String of commands to position the cursor at line L, column
     C, relative to display memory.  Both parameters are origin-zero.
     This capability is present only in terminals where there is a
     difference between screen-relative and memory-relative addressing, and
     not even in all such terminals.

`ch'
     String of commands to position the cursor at column C in the
     same line it is on.  This is a special case of `cm' in which the
     vertical position is not changed.  The `ch' capability is
     provided only when it is faster to output than `cm' would be in
     this special case.  Programs should not assume most display terminals
     have `ch'.

`cv'
     String of commands to position the cursor at line L in the same
     column.  This is a special case of `cm' in which the horizontal
     position is not changed.  The `cv' capability is provided only
     when it is faster to output than `cm' would be in this special
     case.  Programs should not assume most display terminals have
     `cv'.

`sc'
     String of commands to make the terminal save the current cursor
     position.  Only the last saved position can be used.  If this
     capability is present, `rc' should be provided also.  Most
     terminals have neither.

`rc'
     String of commands to make the terminal restore the last saved cursor
     position.  If this capability is present, `sc' should be provided
     also.  Most terminals have neither.

`ff'
     String of commands to advance to the next page, for a hardcopy
     terminal.

`ta'
     String of commands to move the cursor right to the next hardware tab
     stop column.  Missing if the terminal does not have any kind of
     hardware tabs.  Do not send this command if the kernel's terminal
     modes say that the kernel is expanding tabs into spaces.

`bt'
     String of commands to move the cursor left to the previous hardware
     tab stop column.  Missing if the terminal has no such ability; many
     terminals do not.  Do not send this command if the kernel's terminal
     modes say that the kernel is expanding tabs into spaces.

The following obsolete capabilities should be included in terminal
descriptions when appropriate, but should not be looked at by new programs.

`nc'
     Flag whose presence means the terminal does not support the ASCII
     carriage return character as `cr'.  This flag is needed because
     old programs assume, when the `cr' capability is missing, that
     ASCII carriage return can be used for the purpose.  We use `nc'
     to tell the old programs that carriage return may not be used.

     New programs should not assume any default for `cr', so they need
     not look at `nc'.  However, descriptions should contain `nc'
     whenever they do not contain `cr'.

`xt'
     Flag whose presence means that the ASCII tab character may not be used
     for cursor motion.  This flag exists because old programs assume, when
     the `ta' capability is missing, that ASCII tab can be used for
     the purpose.  We use `xt' to tell the old programs not to use tab.

     New programs should not assume any default for `ta', so they need
     not look at `xt' in connection with cursor motion.  Note that
     `xt' also has implications for standout mode (*Note Standout::).
     It is obsolete in regard to cursor motion but not in regard to
     standout.

     In fact, `xt' means that the terminal is a Teleray 1061.

`bc'
     Very obsolete alternative name for the `le' capability.

`bs'
     Flag whose presence means that the ASCII character backspace may be
     used to move the cursor left.  Obsolete; look at `le' instead.

`nl'
     Obsolete capability which is a string that can either be used to move
     the cursor down or to scroll.  The same string must scroll when used
     on the bottom line and move the cursor when used on any other line.
     New programs should use `do' or `sf', and ignore `nl'.

     If there is no `nl' capability, some old programs assume they can
     use the newline character for this purpose.  These programs follow a
     bad practice, but because they exist, it is still desirable to define
     the `nl' capability in a terminal description if the best way to
     move down is *not* a newline.


File: termcap  Node: Wrapping, Prev: Cursor Motion, Up: Capabilities, Next: Scrolling

Wrapping
========

"Wrapping" means moving the cursor from the right margin to the left
margin of the following line.  Some terminals wrap automatically when a
graphic character is output in the last column, while others do not.  Most
application programs that use termcap need to know whether the terminal
wraps.  There are two special flag capabilities to describe what the
terminal does when a graphic character is output in the last column.

`am'
     Flag whose presence means that writing a character in the last column
     causes the cursor to wrap to the beginning of the next line.

     If `am' is not present, writing in the last column leaves the
     cursor at the place where the character was written.

     Writing in the last column of the last line should be avoided on
     terminals with `am', as it may or may not cause scrolling to
     occur (*Note Scrolling::).  Scrolling is surely not what you would
     intend.

     If your program needs to check the `am' flag, then it also needs
     to check the `xn' flag which indicates that wrapping happens in a
     strange way.  Many common terminals have the `xn' flag.

`xn'
     Flag whose presence means that the cursor wraps in a strange way.  At
     least two distinct kinds of strange behavior are known; the termcap
     data base does not contain anything to distinguish the two.

     On Concept-100 terminals, output in the last column wraps the cursor
     almost like an ordinary `am' terminal.  But if the next thing
     output is a newline, it is ignored.

     DEC VT-100 terminals (when the wrap switch is on) do a different
     strange thing: the cursor wraps only if the next thing output is
     another graphic character.  In fact, the wrap occurs when the
     following graphic character is received by the terminal, before the
     character is placed on the screen.

     On both of these terminals, after writing in the last column a
     following graphic character will be displayed in the first column of
     the following line.  But the effect of relative cursor motion
     characters such as newline or backspace at such a time depends on the
     terminal.  The effect of erase or scrolling commands also depends on
     the terminal.  You can't assume anything about what they will do on a
     terminal that has `xn'.  So, to be safe, you should never do
     these things at such a time on such a terminal.

     To be sure of reliable results on a terminal which has the `xn'
     flag, output a `cm' absolute positioning command after writing in
     the last column.  Another safe thing to do is to output carriage-return
     newline, which will leave the cursor at the beginning of the following
     line.


File: termcap  Node: Scrolling, Prev: Wrapping, Up: Capabilities, Next: Windows

Scrolling
=========

"Scrolling" means moving the contents of the screen up or down one or
more lines.  Moving the contents up is "forward scrolling"; moving them
down is "reverse scrolling".

Scrolling happens after each line of output during ordinary output on most
display terminals.  But in an application program that uses termcap for
random-access output, scrolling happens only when explicitly requested with
the commands in this section.

Some terminals have a "scroll region" feature.  This lets you limit
the effect of scrolling to a specified range of lines.  Lines outside the
range are unaffected when scrolling happens.  The scroll region feature
is available if either `cs' or `cS' is present.

`sf'
     String of commands to scroll the screen one line up, assuming it is
     output with the cursor at the beginning of the bottom line.

`sr'
     String of commands to scroll the screen one line down, assuming it is
     output with the cursor at the beginning of the top line.

`SF'
     String of commands to scroll the screen N lines up, assuming it
     is output with the cursor at the beginning of the bottom line.

`SR'
     String of commands to scroll the screen N line down, assuming it
     is output with the cursor at the beginning of the top line.

`cs'
     String of commands to set the scroll region.  This command takes two
     parameters, START and END, which are the line numbers
     (origin-zero) of the first line to include in the scroll region and of
     the last line to include in it.  When a scroll region is set,
     scrolling is limited to the specified range of lines; lines outside
     the range are not affected by scroll commands.

     Do not try to move the cursor outside the scroll region.  The region
     remains set until explicitly removed.  To remove the scroll region,
     use another `cs' command specifying the full height of the
     screen.

     The cursor position is undefined after the `cs' command is set,
     so position the cursor with `cm' immediately afterward.

`cS'
     String of commands to set the scroll region using parameters in
     different form.  The effect is the same as if `cs' were used.
     Four parameters are required:

       1. Total number of lines on the screen.
       2. Number of lines above desired scroll region.
       3. Number of lines below (outside of) desired scroll region.
       4. Total number of lines on the screen, the same as the first parameter.

     This capability is a GNU extension that was invented to allow the Ann
     Arbor Ambassador's scroll-region command to be described; it could
     also be done by putting non-Unix `%'-sequences into a `cs'
     string, but that would have confused Unix programs that used the
     `cs' capability with the Unix termcap.  Currently only GNU Emacs
     uses the `cS' capability.

`ns'
     Flag which means that the terminal does not normally scroll for
     ordinary sequential output.  For modern terminals, this means that
     outputting a newline in ordinary sequential output with the cursor on
     the bottom line wraps to the top line.  For some obsolete terminals,
     other things may happen.

     The terminal may be able to scroll even if it does not normally do so.
     If the `sf' capability is provided, it can be used for scrolling
     regardless of `ns'.

`da'
     Flag whose presence means that lines scrolled up off the top of the
     screen may come back if scrolling down is done subsequently.

     The `da' and `db' flags do not, strictly speaking, affect
     how to scroll.  But programs that scroll usually need to clear the
     lines scrolled onto the screen, if these flags are present.

`db'
     Flag whose presence means that lines scrolled down off the bottom of
     the screen may come back if scrolling up is done subsequently.

`lm'
     Numeric value, the number of lines of display memory that the terminal
     has.  A value of zero means that the terminal has more display memory
     than can fit on the screen, but no fixed number of lines.  (The number
     of lines may depend on the amount of text in each line.)

Any terminal description that defines `SF' should also define `sf';
likewise for `SR' and `sr'.  However, many terminals can only scroll by
one line at a time, so it is common to find `sf' and not `SF', or `sr'
without `SR'.

Therefore, all programs that use the scrolling facilities should be
prepared to work with `sf' in the case that `SF' is absent, and likewise
with `sr'.  On the other hand, an application program that uses only
`sf' and not `SF' is acceptable, though slow on some terminals.

When outputting a scroll command with `tputs', the NLINES
argument should be the total number of lines in the portion of the screen
being scrolled.  Very often these commands require padding proportional to
this number of lines.  *Note Padding::.


File: termcap  Node: Windows, Prev: Scrolling, Up: Capabilities, Next: Clearing

Windows
=======

A "window", in termcap, is a rectangular portion of the screen to which
all display operations are restricted.  Wrapping, clearing, scrolling,
insertion and deletion all operate as if the specified window were all the
screen there was.

`wi'
     String of commands to set the terminal output screen window.
     This string requires four parameters, all origin-zero:
       1. The first line to include in the window.
       2. The last line to include in the window.
       3. The first column to include in the window.
       4. The last column to include in the window.

Most terminals do not support windows.


File: termcap  Node: Clearing, Prev: Windows, Up: Capabilities, Next: Insdel Line

Clearing Parts of the Screen
============================

There are several terminal capabilities for clearing parts of the screen
to blank.  All display terminals support the `cl' string, and most
display terminals support all of these capabilities.

`cl'
     String of commands to clear the entire screen and position the cursor
     at the upper left corner.

`cd'
     String of commands to clear the line the cursor is on, and all the
     lines below it, down to the bottom of the screen.  This command string
     should be used only with the cursor in column zero; their effect is
     undefined if the cursor is elsewhere.

`ce'
     String of commands to clear from the cursor to the end of the current
     line.

`ec'
     String of commands to clear N characters, starting with the
     character that the cursor is on.  This command string is expected to
     leave the cursor position unchanged.  The parameter N should never
     be large enough to reach past the right margin; the effect of such a
     large parameter would be undefined.

Clear to end of line (`ce') is extremely important in programs that
maintain an updating display.  Nearly all display terminals support this
operation, so it is acceptable for a an application program to refuse to
work if `ce' is not present.  However, if you do not want this
limitation, you can accomplish clearing to end of line by outputting spaces
until you reach the right margin.  In order to do this, you must know the
current horizontal position.  Also, this technique assumes that writing a
space will erase.  But this happens to be true on all the display terminals
that fail to support `ce'.


File: termcap  Node: Insdel Line, Prev: Clearing, Up: Capabilities, Next: Insdel Char

Insert/Delete Line
==================

"Inserting a line" means creating a blank line in the middle
of the screen, and pushing the existing lines of text apart.  In fact,
the lines above the insertion point do not change, while the lines below
move down, and one is normally lost at the bottom of the screen.

"Deleting a line" means causing the line to disappear from the screen,
closing up the gap by moving the lines below it upward.  A new line
appears at the bottom of the screen.  Usually this line is blank, but
on terminals with the `db' flag it may be a line previously moved
off the screen bottom by scrolling or line insertion.

Insertion and deletion of lines is useful in programs that maintain an
updating display some parts of which may get longer or shorter.  They are
also useful in editors for scrolling parts of the screen, and for
redisplaying after lines of text are killed or inserted.

Many terminals provide commands to insert or delete a single line at the
cursor position.  Some provide the ability to insert or delete several
lines with one command, using the number of lines to insert or delete as a
parameter.  Always move the cursor to column zero before using any of
these commands.

`al'
     String of commands to insert a blank line before the line the cursor
     is on.  The existing line, and all lines below it, are moved down.
     The last line in the screen (or in the scroll region, if one is set)
     disappears and in most circumstances is discarded.  It may not be
     discarded if the `db' is present (*Note Scrolling::).

     The cursor must be at the left margin before this command is used.
     This command does not move the cursor.

`dl'
     String of commands to delete the line the cursor is on.  The following
     lines move up, and a blank line appears at the bottom of the screen
     (or bottom of the scroll region).  If the terminal has the `db'
     flag, a nonblank line previously pushed off the screen bottom may
     reappear at the bottom.

     The cursor must be at the left margin before this command is used.
     This command does not move the cursor.

`AL'
     String of commands to insert N blank lines before the line that
     the cursor is on.  It is like `al' repeated N times, except
     that it is as fast as one `al'.

`DL'
     String of commands to delete N lines starting with the line that
     the cursor is on.  It is like `dl' repeated N times, except
     that it is as fast as one `dl'.

Any terminal description that defines `AL' should also define `al';
likewise for `DL' and `dl'.  However, many terminals can only insert or
delete one line at a time, so it is common to find `al' and not `AL', or
`dl' without `DL'.

Therefore, all programs that use the insert and delete facilities should
be prepared to work with `al' in the case that `AL' is absent, and
likewise with `dl'.  On the other hand, it is acceptable to write an
application that uses only `al' and `dl' and does not look for `AL' or
`DL' at all.

If a terminal does not support line insertion and deletion directly,
but does support a scroll region, the effect of insertion and deletion
can be obtained with scrolling.  However, it is up to the individual
user program to check for this possibility and use the scrolling
commands to get the desired result.  It is fairly important to implement
this alternate strategy, since it is the only way to get the effect of
line insertion and deletion on the popular VT100 terminal.

Insertion and deletion of lines is affected by the scroll region on
terminals that have a settable scroll region.  This is useful when it is
desirable to move any few consecutive lines up or down by a few lines.
*Note Scrolling::.

The line pushed off the bottom of the screen is not lost if the terminal
has the `db' flag capability; instead, it is pushed into display
memory that does not appear on the screen.  This is the same thing that
happens when scrolling pushes a line off the bottom of the screen.
Either reverse scrolling or deletion of a line can bring the apparently
lost line back onto the bottom of the screen.  If the terminal has the
scroll region feature as well as `db', the pushed-out line really
is lost if a scroll region is in effect.

When outputting an insert or delete command with `tputs', the
NLINES argument should be the total number of lines from the cursor
to the bottom of the screen (or scroll region).  Very often these commands
require padding proportional to this number of lines.  *Note Padding::.

For `AL' and `DL' the NLINES argument should *not*
depend on the number of lines inserted or deleted; only the total number of
lines affected.  This is because it is just as fast to insert two or
N lines with `AL' as to insert one line with `al'.


File: termcap  Node: Insdel Char, Prev: Insdel Line, Up: Capabilities, Next: Standout

Insert/Delete Character
=======================

"Inserting a character" means creating a blank space in the middle of a
line, and pushing the rest of the line rightward.  The character in the
rightmost column is lost.

"Deleting a character" means causing the character to disappear from
the screen, closing up the gap by moving the rest of the line leftward.  A
blank space appears in the rightmost column.

Insertion and deletion of characters is useful in programs that maintain an
updating display some parts of which may get longer or shorter.  It is also
useful in editors for redisplaying the results of editing within a line.

Many terminals provide commands to insert or delete a single character at
the cursor position.  Some provide the ability to insert or delete several
characters with one command, using the number of characters to insert or
delete as a parameter.

Many terminals provide an insert mode in which outputting a graphic
character has the added effect of inserting a position for that character.
A special command string is used to enter insert mode and another is used
to exit it.  The reason for designing a terminal with an insert mode rather
than an insert command is that inserting character positions is usually
followed by writing characters into them.  With insert mode, this is as
fast as simply writing the characters, except for the fixed overhead of
entering and leaving insert mode.  However, when the line speed is great
enough, padding may be required for the graphic characters output in insert
mode.

Some terminals require you to enter insert mode and then output a special
command for each position to be inserted.  Or they may require special
commands to be output before or after each graphic character to be
inserted.

Deletion of characters is usually accomplished by a straightforward command
to delete one or several positions; but on some terminals, it is necessary
to enter a special delete mode before using the delete command, and leave
delete mode afterward.  Sometimes delete mode and insert mode are the same
mode.

Some terminals make a distinction between character positions in which a
space character has been output and positions which have been cleared.  On
these terminals, the effect of insert or delete character runs to the first
cleared position rather than to the end of the line.  In fact, the effect
may run to more than one line if there is no cleared position to stop the
shift on the first line.  These terminals are identified by the `in'
flag capability.

On terminals with the `in' flag, the technique of skipping over
characters that you know were cleared, and then outputting text later on in
the same line, causes later insert and delete character operations on that
line to do nonstandard things.  A program that has any chance of doing this
must check for the `in' flag and must be careful to write explicit
space characters into the intermediate columns when `in' is present.

A plethora of terminal capabilities are needed to describe all of this
complexity.  Here is a list of them all.  Following the list, we present
an algorithm for programs to use to take proper account of all of these
capabilities.

`im'
     String of commands to enter insert mode.

     If the terminal has no special insert mode, but it can insert
     characters with a special command, `im' should be defined with a
     null value, because the `vi' editor assumes that insertion of a
     character is impossible if `im' is not provided.

     New programs should not act like `vi'.  They should pay attention
     to `im' only if it is defined.

`ei'
     String of commands to leave insert mode.  This capability must be
     present if `im' is.

     On a few old terminals the same string is used to enter and exit
     insert mode.  This string turns insert mode on if it was off, and off
     it it was on.  You can tell these terminals because the `ei'
     string equals the `im' string.  If you want to support these
     terminals, you must always remember accurately whether insert mode is
     in effect.  However, these terminals are obsolete, and it is
     reasonable to refuse to support them.  On all modern terminals, you
     can safely output `ei' at any time to ensure that insert mode is
     turned off.

`ic'
     String of commands to insert one character position at the cursor.
     The cursor does not move.

     If outputting a graphic character while in insert mode is sufficient
     to insert the character, then the `ic' capability should be
     defined with a null value.

     If your terminal offers a choice of ways to insert---either use insert
     mode or use a special command---then define `im' and do not define
     `ic', since this gives the most efficient operation when several
     characters are to be inserted.  *Do not* define both strings, for
     that means that *both* must be used each time insertion is done.

`ip'
     String of commands to output following an inserted graphic character
     in insert mode.  Often it is used just for a padding spec, when padding
     is needed after an inserted character (*Note Padding::).

`IC'
     String of commands to insert N character positions at and after
     the cursor.  It has the same effect as repeating the `ic' string
     and a space, N times.

     If `IC' is provided, application programs may use it without first
     entering insert mode.

`mi'
     Flag whose presence means it is safe to move the cursor while in insert
     mode and assume the terminal remains in insert mode.

`in'
     Flag whose presence means that the terminal distinguishes between
     character positions in which space characters have been output and
     positions which have been cleared.

An application program can assume that the terminal can do character
insertion if *any one of* the capabilities `IC', `im',
`ic' or `ip' is provided.

To insert N blank character positions, move the cursor to the place
to insert them and follow this algorithm:

  1. If an `IC' string is provided, output it with parameter N
     and you are finished.  Otherwise (or if you don't want to bother to
     look for an `IC' string) follow the remaining steps.

  2. Output the `im' string, if there is one, unless the terminal is
     already in insert mode.

  3. Repeat steps 4 through 6, N times.

  4. Output the `ic' string if any.

  5. Output a space.

  6. Output the `ip' string if any.

  7. Output the `ei' string, eventually, to exit insert mode.  There
     is no need to do this right away.  If the `mi' flag is present,
     you can move the cursor and the cursor will remain in insert mode;
     then you can do more insertion elsewhere without reentering insert
     mode.

To insert N graphic characters, position the cursor and follow this
algorithm:

  1. If an `IC' string is provided, output it with parameter N,
     then output the graphic characters, and you are finished.  Otherwise
     (or if you don't want to bother to look for an `IC' string)
     follow the remaining steps.

  2. Output the `im' string, if there is one, unless the terminal is
     already in insert mode.

  3. For each character to be output, repeat steps 4 through 6.

  4. Output the `ic' string if any.

  5. Output the next graphic character.

  6. Output the `ip' string if any.

  7. Output the `ei' string, eventually, to exit insert mode.  There
     is no need to do this right away.  If the `mi' flag is present,
     you can move the cursor and the cursor will remain in insert mode;
     then you can do more insertion elsewhere without reentering insert
     mode.

Note that this is not the same as the original Unix termcap specifications
in one respect: it assumes that the `IC' string can be used without
entering insert mode.  This is true as far as I know, and it allows you be
able to avoid entering and leaving insert mode, and also to be able to
avoid the inserted-character padding after the characters that go into the
inserted positions.

Deletion of characters is less complicated; deleting one column is done by
outputting the `dc' string.  However, there may be a delete mode that
must be entered with `dm' in order to make `dc' work.

`dc'
     String of commands to delete one character position at the cursor.  If
     `dc' is not present, the terminal cannot delete characters.

`DC'
     String of commands to delete N characters starting at the cursor.
     It has the same effect as repeating the `dc' string N times.
     Any terminal description that has `DC' also has `dc'.

`dm'
     String of commands to enter delete mode.  If not present, there is no
     delete mode, and `dc' can be used at any time (assuming there is
     a `dc').

`ed'
     String of commands to exit delete mode.  This must be present if
     `dm' is.

To delete N character positions, position the cursor and follow these
steps:

  1. If the `DC' string is present, output it with parameter N
     and you are finished.  Otherwise, follow the remaining steps.

  2. Output the `dm' string, unless you know the terminal is already
     in delete mode.

  3. Output the `dc' string N times.

  4. Output the `ed' string eventually.  If the flag capability
     `mi' is present, you can move the cursor and do more deletion
     without leaving and reentering delete mode.

As with the `IC' string, we have departed from the original termcap
specifications by assuming that `DC' works without entering delete
mode even though `dc' would not.

If the `dm' and `im' capabilities are both present and have the
same value, it means that the terminal has one mode for both insertion and
deletion.  It is useful for a program to know this, because then it can do
insertions after deletions, or vice versa, without leaving insert/delete
mode and reentering it.


File: termcap  Node: Standout, Prev: Insdel Char, Up: Capabilities, Next: Underlining

Standout and Appearance Modes
=============================

"Appearance modes" are modifications to the ways characters are
displayed.  Typical appearance modes include reverse video, dim, bright,
blinking, underlined, invisible, and alternate character set.  Each kind of
terminal supports various among these, or perhaps none.

For each type of terminal, one appearance mode or combination of them that
looks good for highlighted text is chosen as the "standout mode".  The
capabilities `so' and `se' say how to enter and leave standout
mode.  Programs that use appearance modes only to highlight some text
generally use the standout mode so that they can work on as many terminals
as possible.  Use of specific appearance modes other than "underlined"
and "alternate character set" is rare.

Terminals that implement appearance modes fall into two general classes as
to how they do it.

In some terminals, the presence or absence of any appearance mode is
recorded separately for each character position.  In these terminals, each
graphic character written is given the appearance modes current at the time
it is written, and keeps those modes until it is erased or overwritten.
There are special commands to turn the appearance modes on or off for
characters to be written in the future.

In other terminals, the change of appearance modes is represented by a
marker that belongs to a certain screen position but affects all following
screen positions until the next marker.  These markers are traditionally
called "magic cookies".

The same capabilities (`so', `se', `mb' and so on) for
turning appearance modes on and off are used for both magic-cookie
terminals and per-character terminals.  On magic cookie terminals, these
give the commands to write the magic cookies.  On per-character terminals,
they change the current modes that affect future output and erasure.  Some
simple applications can use these commands without knowing whether or not
they work by means of cookies.

However, a program that maintains and updates a display needs to know
whether the terminal uses magic cookies, and exactly what their effect is.
This information comes from the `sg' capability.

The `sg' capability is a numeric capability whose presence indicates
that the terminal uses magic cookies for appearance modes.  Its value is
the number of character positions that a magic cookie occupies.  Usually
the cookie occupies one or more character positions on the screen, and these
character positions are displayed as blank, but in some terminals the
cookie has zero width.

The `sg' capability describes both the magic cookie to turn standout
on and the cookie to turn it off.  This makes the assumption that both
kinds of cookie have the same width on the screen.  If that is not true,
the narrower cookie must be "widened" with spaces until it has the same
width as the other.

On some magic cookie terminals, each line always starts with normal
display; in other words, the scope of a magic cookie never extends over
more than one line.  But on other terminals, one magic cookie affects all
the lines below it unless explicitly canceled.  Termcap does not define any
way to distinguish these two ways magic cookies can work.  To be safe, it
is best to put a cookie at the beginning of each line.

On some per-character terminals, standout mode or other appearance modes
may be canceled by moving the cursor.  On others, moving the cursor has no
effect on the state of the appearance modes.  The latter class of terminals
are given the flag capability `ms' ("can move in standout").  All
programs that might have occasion to move the cursor while appearance modes
are turned on must check for this flag; if it is not present, they should
reset appearance modes to normal before doing cursor motion.

A program that has turned on only standout mode should use `se' to
reset the standout mode to normal.  A program that has turned on only
alternate character set mode should use `ae' to return it to normal.
If it is possible that any other appearance modes are turned on, use the
`me' capability to return them to normal.

Note that the commands to turn on one appearance mode, including `so'
and `mb' ... `mr', if used while some other appearance modes
are turned on, may combine the two modes on some terminals but may turn off
the mode previously enabled on other terminals.  This is because some
terminals do not have a command to set or clear one appearance mode without
changing the others.  Programs should not attempt to use appearance modes
in combination except with `sa', and when switching from one single
mode to another should always turn off the previously enabled mode and then
turn on the new desired mode.

On some old terminals, the `so' and `se' commands may be the same
command, which has the effect of turning standout on if it is off, or off
it is on.  It is therefore risky for a program to output extra `se'
commands for good measure.  Fortunately, all these terminals are obsolete.

Programs that update displays in which standout-text may be replaced with
non-standout text must check for the `xs' flag.  In a per-character
terminal, this flag says that the only way to remove standout once written is
to clear that portion of the line with the `ce' string or something
even more powerful (*Note Clearing::); just writing new characters at those
screen positions will not change the modes in effect there.  In a magic
cookie terminal, `xs' says that the only way to remove a cookie is to
clear a portion of the line that includes the cookie; writing a different
cookie at the same position does not work.

Such programs must also check for the `xt' flag, which means that the
terminal is a Teleray 1061.  On this terminal it is impossible to position
the cursor at the front of a magic cookie, so the only two ways to remove a
cookie are (1) to delete the line it is on or (2) to position the cursor at
least one character before it (possibly on a previous line) and output the
`se' string, which on these terminals finds and removes the next
`so' magic cookie on the screen.  (It may also be possible to remove a
cookie which is not at the beginning of a line by clearing that line.)  The
`xt' capability also has implications for the use of tab characters,
but in that regard it is obsolete (*Note Cursor Motion::).

`so'
     String of commands to enter standout mode.

`se'
     String of commands to leave standout mode.

`sg'
     Numeric capability, the width on the screen of the magic cookie.  This
     capability is absent in terminals that record appearance modes
     character by character.

`ms'
     Flag whose presence means that it is safe to move the cursor while the
     appearance modes are not in the normal state.  If this flag is absent,
     programs should always reset the appearance modes to normal before
     moving the cursor.

`xs'
     Flag whose presence means that the only way to reset appearance modes
     already on the screen is to clear to end of line.  On a per-character
     terminal, you must clear the area where the modes are set.  On a magic
     cookie terminal, you must clear an area containing the cookie.
     See the discussion above.

`xt'
     Flag whose presence means that the cursor cannot be positioned right
     in front of a magic cookie, and that `se' is a command to delete
     the next magic cookie following the cursor.  See discussion above.

`mb'
     String of commands to enter blinking mode.

`md'
     String of commands to enter double-bright mode.

`mh'
     String of commands to enter half-bright mode.

`mk'
     String of commands to enter invisible mode.

`mp'
     String of commands to enter protected mode.

`mr'
     String of commands to enter reverse-video mode.

`me'
     String of commands to turn off all appearance modes, including
     standout mode and underline mode.  On some terminals it also turns off
     alternate character set mode; on others, it may not.  This capability
     must be present if any of `mb' ... `mr' is present.

`as'
     String of commands to turn on alternate character set mode.  This mode
     assigns some or all graphic characters an alternate picture on the
     screen.  There is no standard as to what the alternate pictures look
     like.

`ae'
     String of commands to turn off alternate character set mode.

`sa'
     String of commands to turn on an arbitrary combination of appearance
     modes.  It accepts 9 parameters, each of which controls a particular
     kind of appearance mode.  A parameter should be 1 to turn its appearance
     mode on, or zero to turn that mode off.  Most terminals do not support
     the `sa' capability, even among those that do have various
     appearance modes.

     The nine parameters are, in order, STANDOUT, UNDERLINE,
     REVERSE, BLINK, HALF-BRIGHT, DOUBLE-BRIGHT,
     BLANK, PROTECT, ALT CHAR SET.


File: termcap  Node: Underlining, Prev: Standout, Up: Capabilities, Next: Cursor Visibility

Underlining
===========

Underlining on most terminals is a kind of appearance mode, much like
standout mode.  Therefore, it may be implemented using magic cookies or as
a flag in the terminal whose current state affects each character that is
output.  *Note Standout::, for a full explanation.

The `ug' capability is a numeric capability whose presence indicates
that the terminal uses magic cookies for underlining.  Its value is the
number of character positions that a magic cookie for underlining occupies;
it is used for underlining just as `sg' is used for standout.  Aside
from the simplest applications, it is impossible to use underlining
correctly without paying attention to the value of `ug'.

`us'
     String of commands to turn on underline mode or to output a magic cookie
     to start underlining.

`ue'
     String of commands to turn off underline mode or to output a magic
     cookie to stop underlining.

`ug'
     Width of magic cookie that represents a change of underline mode;
     or missing, if the terminal does not use a magic cookie for this.

`ms'
     Flag whose presence means that it is safe to move the cursor while the
     appearance modes are not in the normal state.  Underlining is an
     appearance mode.  If this flag is absent, programs should always turn
     off underlining before moving the cursor.

There are two other, older ways of doing underlining: there can be a
command to underline a single character, or the output of `_', the
ASCII underscore character, as an overstrike could cause a character to be
underlined.  New programs need not bother to handle these capabilities
unless the author cares strongly about the obscure terminals which support
them.  However, terminal descriptions should provide these capabilities
when appropriate.

`uc'
     String of commands to underline the character under the cursor, and
     move the cursor right.

`ul'
     Flag whose presence means that the terminal can underline by
     overstriking an underscore character (`_'); some terminals can do
     this even though they do not support overstriking in general.  An
     implication of this flag is that when outputting new text to overwrite
     old text, underscore characters must be treated specially lest they
     underline the old text instead.



File: termcap  Node: Cursor Visibility, Prev: Underlining, Up: Capabilities, Next: Bell

Cursor Visibility
=================

Some terminals have the ability to make the cursor invisible, or to enhance
it.  Enhancing the cursor is often done by programs that plan to use the
cursor to indicate to the user a position of interest that may be anywhere
on the screen---for example, the Emacs editor enhances the cursor on entry.
Such programs should always restore the cursor to normal on exit.

`vs'
     String of commands to enhance the cursor.

`vi'
     String of commands to make the cursor invisible.

`ve'
     String of commands to return the cursor to normal.

If you define either `vs' or `vi', you must also define `ve'.


File: termcap  Node: Bell, Prev: Cursor Visibility, Up: Capabilities, Next: Keypad

Bell
====

Here we describe commands to make the terminal ask for the user to pay
attention to it.

`bl'
     String of commands to cause the terminal to make an audible sound.  If
     this capability is absent, the terminal has no way to make a suitable
     sound.

`vb'
     String of commands to cause the screen to flash to attract attention
     ("visible bell").  If this capability is absent, the terminal has no
     way to do such a thing.


File: termcap  Node: Keypad, Prev: Bell, Up: Capabilities, Next: Meta Key

Keypad and Function Keys
========================

Many terminals have arrow and function keys that transmit specific
character sequences to the computer.  Since the precise sequences used
depend on the terminal, termcap defines capabilities used to say what the
sequences are.  Unlike most termcap string-valued capabilities, these are
not strings of commands to be sent to the terminal, rather strings that
are received from the terminal.

Programs that expect to use keypad keys should check, initially, for a
`ks' capability and send it, to make the keypad actually transmit.
Such programs should also send the `ke' string when exiting.

`ks'
     String of commands to make the function keys transmit.  If this
     capability is not provided, but the others in this section are,
     programs may assume that the function keys always transmit.

`ke'
     String of commands to make the function keys work locally.  This
     capability is provided only if `ks' is.

`kl'
     String of input characters sent by typing the left-arrow key.  If this
     capability is missing, you cannot expect the terminal to have a
     left-arrow key that transmits anything to the computer.

`kr'
     String of input characters sent by typing the right-arrow key.

`ku'
     String of input characters sent by typing the up-arrow key.

`kd'
     String of input characters sent by typing the down-arrow key.

`kh'
     String of input characters sent by typing the "home-position" key.

`K1' ... `K5'
     Strings of input characters sent by the five other keys in a 3-by-3
     array that includes the arrow keys, if the keyboard has such a 3-by-3
     array.  Note that one of these keys may be the "home-position" key,
     in which case one of these capabilities will have the same value as
     the `kh' key.

`k0'
     String of input characters sent by function key 10 (or 0, if the terminal
     has one labeled 0).

`k1' ... `k9'
     Strings of input characters sent by function keys 1 through 9,
     provided for those function keys that exist.

`kn'
     Number: the number of numbered function keys, if there are more than
     10.

`l0' ... `l9'
     Strings which are the labels appearing on the keyboard on the keys
     described by the capabilities `k0' ... `l9'.  These capabilities
     should be left undefined if the labels are `f0' or `f10' and `f1'
     ... `f9'.

`kH'
     String of input characters sent by the "home down" key, if there is
     one.

`kb'
     String of input characters sent by the "backspace" key, if there is
     one.

`ka'
     String of input characters sent by the "clear all tabs" key, if there
     is one.

`kt'
     String of input characters sent by the "clear tab stop this column"
     key, if there is one.

`kC'
     String of input characters sent by the "clear screen" key, if there is
     one.

`kD'
     String of input characters sent by the "delete character" key, if
     there is one.

`kL'
     String of input characters sent by the "delete line" key, if there is
     one.

`kM'
     String of input characters sent by the "exit insert mode" key, if
     there is one.

`kE'
     String of input characters sent by the "clear to end of line" key, if
     there is one.

`kS'
     String of input characters sent by the "clear to end of screen" key,
     if there is one.

`kI'
     String of input characters sent by the "insert character" or "enter
     insert mode" key, if there is one.

`kA'
     String of input characters sent by the "insert line" key, if there is
     one.

`kN'
     String of input characters sent by the "next page" key, if there is
     one.

`kP'
     String of input characters sent by the "previous page" key, if there is
     one.

`kF'
     String of input characters sent by the "scroll forward" key, if there
     is one.

`kR'
     String of input characters sent by the "scroll reverse" key, if there
     is one.

`kT'
     String of input characters sent by the "set tab stop in this column"
     key, if there is one.

`ko'
     String listing the other function keys the terminal has.  This is a
     very obsolete way of describing the same information found in the
     `kH' ... `kT' keys.  The string contains a list of two-character
     termcap capability names, separated by commas.  The meaning is that
     for each capability name listed, the terminal has a key which sends
     the string which is the value of that capability.  For example, the
     value `:ko=cl,ll,sf,sr:' says that the terminal has four function
     keys which mean "clear screen", "home down", "scroll forward" and
     "scroll reverse".


File: termcap  Node: Meta Key, Prev: Keypad, Up: Capabilities, Next: Initialization

Meta Key
========

A Meta key is a key on the keyboard that modifies each character you type
by controlling the 0200 bit.  This bit is on if and only if the Meta key is
held down when the character is typed.  Characters typed using the Meta key
are called Meta characters.  Emacs uses Meta characters as editing
commands.

`km'
     Flag whose presence means that the terminal has a Meta key.

`mm'
     String of commands to enable the functioning of the Meta key.

`mo'
     String of commands to disable the functioning of the Meta key.

If the terminal has `km' but does not have `mm' and `mo', it
means that the Meta key always functions.  If it has `mm' and
`mo', it means that the Meta key can be turned on or off.  Send the
`mm' string to turn it on, and the `mo' string to turn it off.
I do not know why one would ever not want it to be on.


File: termcap  Node: Initialization, Prev: Meta Key, Up: Capabilities, Next: Pad Specs

Initialization
==============

`ti'
     String of commands to put the terminal into whatever special modes are
     needed or appropriate for programs that move the cursor
     nonsequentially around the screen.  Programs that use termcap to do
     full-screen display should output this string when they start up.

`te'
     String of commands to undo what is done by the `ti' string.
     Programs that output the `ti' string on entry should output this
     string when they exit.

`is'
     String of commands to initialize the terminal for each login session.

`if'
     String which is the name of a file containing the string of commands
     to initialize the terminal for each session of use.  Normally `is'
     and `if' are not both used.

`i1'
`i3'
     Two more strings of commands to initialize the terminal for each login
     session.  The `i1' string (if defined) is output before `is'
     or `if', and the `i3' string (if defined) is output after.

     The reason for having three separate initialization strings is to make
     it easier to define a group of related terminal types with slightly
     different initializations.  Define two or three of the strings in the
     basic type; then the other types can override one or two of the
     strings.

`rs'
     String of commands to reset the terminal from any strange mode it may
     be in.  Normally this includes the `is' string (or other commands
     with the same effects) and more.  What would go in the `rs'
     string but not in the `is' string are annoying or slow commands
     to bring the terminal back from strange modes that nobody would
     normally use.

`it'
     Numeric value, the initial spacing between hardware tab stop columns
     when the terminal is powered up.  Programs to initialize the terminal
     can use this to decide whether there is a need to set the tab stops.
     If the initial width is 8, well and good; if it is not 8, then the
     tab stops should be set; if they cannot be set, the kernel is told
     to convert tabs to spaces, and other programs will observe this and do
     likewise.

`ct'
     String of commands to clear all tab stops.

`st'
     String of commands to set tab stop at current cursor column on all
     lines.


File: termcap  Node: Pad Specs, Prev: Initialization, Up: Capabilities, Next: Status Line

Padding Capabilities
====================

There are two terminal capabilities that exist just to explain the proper
way to obey the padding specifications in all the command string
capabilities.  One, `pc', must be obeyed by all termcap-using
programs.

`pb'
     Numeric value, the lowest baud rate at which padding is actually
     needed.  Programs may check this and refrain from doing any padding at
     lower speeds.

`pc'
     String of commands for padding.  The first character of this string is
     to be used as the pad character, instead of using null characters for
     padding.  If `pc' is not provided, use null characters.  Every
     program that uses termcap must look up this capability and use it to
     set the variable `PC' that is used by `tputs'.
     *Note Padding::.

Some termcap capabilities exist just to specify the amount of padding that
the kernel should give to cursor motion commands used in ordinary
sequential output.

`dC'
     Numeric value, the number of msec of padding needed for the
     carriage-return character.

`dN'
     Numeric value, the number of msec of padding needed for the newline
     (linefeed) character.

`dB'
     Numeric value, the number of msec of padding needed for the backspace
     character.

`dF'
     Numeric value, the number of msec of padding needed for the formfeed
     character.

`dT'
     Numeric value, the number of msec of padding needed for the tab
     character.

In some systems, the kernel uses the above capabilities; in other systems,
the kernel uses the paddings specified in the string capabilities
`cr', `sf', `le', `ff' and `ta'.  Descriptions of
terminals which require such padding should contain the `dC' ...
`dT' capabilities and also specify the appropriate padding in the
corresponding string capabilities.  Since no modern terminals require
padding for ordinary sequential output, you probably won't need to do
either of these things.


File: termcap  Node: Status Line, Prev: Pad Specs, Up: Capabilities, Next: Half-Line

Status Line
===========

A "status line" is a line on the terminal that is not used for ordinary
display output but instead used for a special message.  The intended use is
for a continuously updated description of what the user's program is doing,
and that is where the name "status line" comes from, but in fact it could
be used for anything.  The distinguishing characteristic of a status line
is that ordinary output to the terminal does not affect it; it changes only
if the special status line commands of this section are used.

`hs'
     Flag whose presence means that the terminal has a status line.  If a
     terminal description specifies that there is a status line, it must
     provide the `ts' and `fs' capabilities.

`ts'
     String of commands to move the terminal cursor into the status line.
     Usually these commands must specifically record the old cursor
     position for the sake of the `fs' string.

`fs'
     String of commands to move the cursor back from the status line to its
     previous position (outside the status line).

`es'
     Flag whose presence means that other display commands work while
     writing the status line.  In other words, one can clear parts of it,
     insert or delete characters, move the cursor within it using `ch'
     if there is a `ch' capability, enter and leave standout mode, and
     so on.

`ds'
     String of commands to disable the display of the status line.  This
     may be absent, if there is no way to disable the status line display.

`ws'
     Numeric value, the width of the status line.  If this capability is
     absent in a terminal that has a status line, it means the status line
     is the same width as the other lines.

     Note that the value of `ws' is sometimes as small as 8.


File: termcap  Node: Half-Line, Prev: Status Line, Up: Capabilities, Next: Printer

Half-Line Motion
================

Some terminals have commands for moving the cursor vertically by half-lines,
useful for outputting subscripts and superscripts.  Mostly it is hardcopy
terminals that have such features.

`hu'
     String of commands to move the cursor up half a line.  If the terminal
     is a display, it is your responsibility to avoid moving up past the
     top line; however, most likely the terminal that supports this is a
     hardcopy terminal and there is nothing to be concerned about.

`hd'
     String of commands to move the cursor down half a line.  If the
     terminal is a display, it is your responsibility to avoid moving down
     past the bottom line, etc.


File: termcap  Node: Printer, Prev: Half-Line, Up: Capabilities

Controlling Printers Attached to Terminals
==========================================

Some terminals have attached hardcopy printer ports.  They may be able to
copy the screen contents to the printer; they may also be able to redirect
output to the printer.  Termcap does not have anything to tell the program
whether the redirected output appears also on the screen; it does on some
terminals but not all.

`ps'
     String of commands to cause the contents of the screen to be printed.
     If it is absent, the screen contents cannot be printed.

`po'
     String of commands to redirect further output to the printer.

`pf'
     String of commands to terminate redirection of output to the printer.
     This capability must be present in the description if `po' is.

`pO'
     String of commands to redirect output to the printer for next N
     characters of output, regardless of what they are.  Redirection will
     end automatically after N characters of further output.  Until
     then, nothing that is output can end redirection, not even the
     `pf' string if there is one.  The number N should not be
     more than 255.

     One use of this capability is to send non-text byte sequences (such as
     bit-maps) to the printer.

Most terminals with printers do not support all of `ps', `po' and
`pO'; any one or two of them may be supported.  To make a program that
can send output to all kinds of printers, it is necessary to check for all
three of these capabilities, choose the most convenient of the ones that
are provided, and use it in its own appropriate fashion.


File: termcap  Node: Summary, Prev: Capabilities, Up: Top, Next: Var Index

Summary of Capability Names
***************************

Here are all the terminal capability names in alphabetical order
with a brief description of each.  For cross references to their definitions,
see the index of capability names (*Note Cap Index::).

`ae'
     String to turn off alternate character set mode.
`al'
     String to insert a blank line before the cursor.
`AL'
     String to insert N blank lines before the cursor.
`am'
     Flag: output to last column wraps cursor to next line.
`as'
     String to turn on alternate character set mode.like.
`bc'
     Very obsolete alternative name for the `le' capability.
`bl'
     String to sound the bell.
`bs'
     Obsolete flag: ASCII backspace may be used for leftward motion.
`bt'
     String to move the cursor left to the previous hardware tab stop column.
`bw'
     Flag: `le' at left margin wraps to end of previous line.
`CC'
     String to change terminal's command character.
`cd'
     String to clear the line the cursor is on, and following lines.
`ce'
     String to clear from the cursor to the end of the line.
`ch'
     String to position the cursor at column C in the same line.
`cl'
     String to clear the entire screen and put cursor at upper left corner.
`cm'
     String to position the cursor at line L, column C.
`CM'
     String to position the cursor at line L, column
     C, relative to display memory.
`co'
     Number: width of the screen.
`cr'
     String to move cursor sideways to left margin.
`cs'
     String to set the scroll region.
`cS'
     Alternate form of string to set the scroll region.
`ct'
     String to clear all tab stops.
`cv'
     String to position the cursor at line L in the same column.
`da'
     Flag: data scrolled off top of screen may be scrolled back.
`db'
     Flag: data scrolled off bottom of screen may be scrolled back.
`dB'
     Obsolete number: msec of padding needed for the backspace character.
`dc'
     String to delete one character position at the cursor.
`dC'
     Obsolete number: msec of padding needed for the carriage-return character.
`DC'
     String to delete N characters starting at the cursor.
`dF'
     Obsolete number: msec of padding needed for the formfeed character.
`dl'
     String to delete the line the cursor is on.
`DL'
     String to delete N lines starting with the cursor's line.
`dm'
     String to enter delete mode.
`dN'
     Obsolete number: msec of padding needed for the newline character.
`do'
     String to move the cursor vertically down one line.
`DO'
     String to move cursor vertically down N lines.
`ds'
     String to disable the display of the status line.
`dT'
     Obsolete number: msec of padding needed for the tab character.
`ec'
     String of commands to clear N characters at cursor.
`ed'
     String to exit delete mode.
`ei'
     String to leave insert mode.
`eo'
     Flag: output of a space can erase an overstrike.
`es'
     Flag: other display commands work while writing the status line.
`ff'
     String to advance to the next page, for a hardcopy terminal.
`fs'
     String to move the cursor back from the status line to its
     previous position (outside the status line).
`gn'
     Flag: this terminal type is generic, not real.
`hc'
     Flag: hardcopy terminal.
`hd'
     String to move the cursor down half a line.
`ho'
     String to position cursor at upper left corner.
`hs'
     Flag: the terminal has a status line.
`hu'
     String to move the cursor up half a line.
`hz'
     Flag: terminal cannot accept `~' as output.
`i1'
     String to initialize the terminal for each login session.
`i3'
     String to initialize the terminal for each login session.
`ic'
     String to insert one character position at the cursor.
`IC'
     String to insert N character positions at the cursor.
`if'
     String naming a file of commands to initialize the terminal.
`im'
     String to enter insert mode.
`in'
     Flag: outputting a space is different from moving over empty positions.
`ip'
     String to output following an inserted character in insert mode.
`is'
     String to initialize the terminal for each login session.
`it'
     Number: initial spacing between hardware tab stop columns.
`k0'
     String of input sent by function key 0 or 10.
`k1 ... k9'
     Strings of input sent by function keys 1 through 9.
`K1 ... K5'
     Strings sent by the five other keys in 3-by-3 array with arrows.
`ka'
     String of input sent by the "clear all tabs" key.
`kA'
     String of input sent by the "insert line" key.
`kb'
     String of input sent by the "backspace" key.
`kC'
     String of input sent by the "clear screen" key.
`kd'
     String of input sent by typing the down-arrow key.
`kD'
     String of input sent by the "delete character" key.
`ke'
     String to make the function keys work locally.
`kE'
     String of input sent by the "clear to end of line" key.
`kF'
     String of input sent by the "scroll forward" key.
`kh'
     String of input sent by typing the "home-position" key.
`kH'
     String of input sent by the "home down" key.
`kI'
     String of input sent by the "insert character" or "enter
     insert mode" key.
`kl'
     String of input sent by typing the left-arrow key.
`kL'
     String of input sent by the "delete line" key.
`km'
     Flag: the terminal has a Meta key.
`kM'
     String of input sent by the "exit insert mode" key.
`kn'
     Numeric value, the number of numbered function keys.
`kN'
     String of input sent by the "next page" key.
`ko'
     Very obsolete string listing the terminal's named function keys.
`kP'
     String of input sent by the "previous page" key.
`kr'
     String of input sent by typing the right-arrow key.
`kR'
     String of input sent by the "scroll reverse" key.
`ks'
     String to make the function keys transmit.
`kS'
     String of input sent by the "clear to end of screen" key.
`kt'
     String of input sent by the "clear tab stop this column" key.
`kT'
     String of input sent by the "set tab stop in this column" key.
`ku'
     String of input sent by typing the up-arrow key.
`l0'
     String on keyboard labelling function key 0 or 10.
`l1 ... l9'
     Strings on keyboard labelling function keys 1 through 9.
`le'
     String to move the cursor left one column.
`LE'
     String to move cursor left N columns.
`li'
     Number: height of the screen.
`ll'
     String to position cursor at lower left corner.
`lm'
     Number: lines of display memory.
`mb'
     String to enter blinking mode.
`md'
     String to enter double-bright mode.
`me'
     String to turn off all appearance modes
`mh'
     String to enter half-bright mode.
`mi'
     Flag: cursor motion in insert mode is safe.
`mk'
     String to enter invisible mode.
`mm'
     String to enable the functioning of the Meta key.
`mo'
     String to disable the functioning of the Meta key.
`mp'
     String to enter protected mode.
`mr'
     String to enter reverse-video mode.
`ms'
     Flag: cursor motion in standout mode is safe.
`nc'
     Obsolete flag: do not use ASCII carriage-return on this terminal.
`nd'
     String to move the cursor right one column.
`nl'
     Obsolete alternative name for the `do' and `sf' capabilities.
`ns'
     Flag: the terminal does not normally scroll for sequential output.
`nw'
     String to move to start of next line, possibly clearing rest of old line.
`os'
     Flag: terminal can overstrike.
`pb'
     Number: the lowest baud rate at which padding is actually needed.
`pc'
     String containing character for padding.
`pf'
     String to terminate redirection of output to the printer.
`po'
     String to redirect further output to the printer.
`pO'
     String to redirect N characters ofoutput to the printer.
`ps'
     String to print the screen on the attached printer.
`rc'
     String to move to last saved cursor position.
`RI'
     String to move cursor right N columns.
`rp'
     String to output character C repeated N times.
`rs'
     String to reset the terminal from any strange modes.
`sa'
     String to turn on an arbitrary combination of appearance modes.
`sc'
     String to save the current cursor position.
`se'
     String to leave standout mode.
`sf'
     String to scroll the screen one line up.
`SF'
     String to scroll the screen N lines up.
`sg'
     Number: width of magic standout cookie.  Absent if magic cookies are
     not used.
`so'
     String to enter standout mode.
`sr'
     String to scroll the screen one line down.
`SR'
     String to scroll the screen N line down.
`st'
     String to set tab stop at current cursor column on all lines.
     programs.
`ta'
     String to move the cursor right to the next hardware tab stop column.
`te'
     String to return terminal to settings for sequential output.
`ti'
     String to initialize terminal for random cursor motion.
`ts'
     String to move the terminal cursor into the status line.
`uc'
     String to underline one character and move cursor right.
`ue'
     String to turn off underline mode
`ug'
     Number: width of underlining magic cookie.  Absent if underlining
     doesn't use magic cookies.
`ul'
     Flag: underline by overstriking with an underscore.
`up'
     String to move the cursor vertically up one line.
`UP'
     String to move cursor vertically up N lines.
`us'
     String to turn on underline mode
`vb'
     String to make the screen flash.
`ve'
     String to return the cursor to normal.
`vi'
     String to make the cursor invisible.
`vs'
     String to enhance the cursor.
`wi'
     String to set the terminal output screen window.
`ws'
     Number: the width of the status line.
`xb'
     Flag: superbee terminal.
`xn'
     Flag: cursor wraps in a strange way.
`xs'
     Flag: clearing a line is the only way to clear the appearance modes of
     positions in that line (or, only way to remove magic cookies on that
     line).
`xt'
     Flag: Teleray 1061; several strange characteristics.