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Text File | 1985-07-08 | 21.2 KB | 462 lines

ANSI.SYS ~~~~~~~~ What is a Device Driver ? Basically, a Device Driver is a special software program used to manage all communications between a device (usually hardware) and the PC. It's helpful to think of a device driver as a "logical" device. To the operating system, this driver is the device. DOS never "sees" the actual device, but accesses the actual device through the driver. In other words, the device driver is an interface. DOS has several "built-in" device drivers that handle such things as the diskette drives, system clock, the console (key- board and display), printer (parallel port) and communications (serial port). There are two (2) types of devices, character and block. Character devices handle I/O in a serial manner like CON, AUX, CLOCK$ and PRN. Character devices can be "opened" to do input and/or output since they have only one name and handle only one physical device. On the other hand, block devices are the hard disk and diskette drives in a system and do random I/O in pieces called blocks (usually the sector size of a disk). These devices are not named like the character devices, rather they are "mapped" alphabetically by drive letter. Block devices can handle several physical units. So a single device driver can be responsible for I/O to several diskette drives and/or hard disks. The CONFIG.SYS file One of the first things things to happen when you "boot" your computer, is that the operating system looks for special information about how it is to configure itself. It expects to find those directions in a text file on the boot disk called CONFIG.SYS. If DOS can't find a CONFIG.SYS file, it sets itself up in a "default" configuration. Think of CONFIG.SYS as containing the first directions you give to DOS. Among other things, those directions may include the names of foreign (non IBM) devices that are to be added to the system. When you add a device to the computer that is non IBM, (and even some that are IBM), you will need a matching software device driver so that it can be integrated into the system. A typical CONFIG.SYS file might look like this. Sample CONFIG.SYS file ----------------------- | DEVICE = MOUSE.SYS | | DEVICE = CLOCK.SYS | | DEVICE = HARDDISK.SYS | | DEVICE = RAMDISK.SYS | ----------------------- The sample file tells DOS to install character (mouse and clock-calendar) and block (a hard disk and a ram disk) devices. Notice that the ram disk is entirely software. No hardware is involved. This is one of the very useful feature of device drivers. To install a new or replacement device in your computer system, one of the steps will include adding a line to the CONFIG.SYS file. ANSI.SYS - A CONsole device driver The ANSI.SYS driver gets its name from the American National Standards Institute (ANSI), which defined a standard method for control of certain terminal characteristics. The effort at standardization was a reaction to the many types of intelligent terminals being manufactured. Unfortunately, ANSI.SYS was not entirely successful: manufacturers having different goals than the committee. In fact, no terminals are ANSI standard, although the DEC VT-100 comes quite close. The central concern of the committee was to define codes in addition to the standard ASCII control codes that could be use to govern terminal characteristics such as cursor and character positioning, character high- lighting and character color. You may know, ASCII is a code that provides for the translation of the standard alphanumeric characters into a binary form for storage and manipu- lation by the computer. Using binary notation, 7-bits can represent any of 128 different values (2 to the 7th) which is more than ample for encoding the 96 standard alphanumeric characters and a few punctuation symbols. The standard ASCII codes (as opposed to the extended IBM set of 256) also include 32 "control characters" (i.e. carriage return, tab, line feed, etc). Control characters generally provide "commands" (as opposed to data) to peripheral devices. For example, a line feed tells a display to move the cursor down 1 line. But 32 characters allow only a total of 32 possible commands, rather limited. What the ANSI committee attempted was to provide a standard syntax which would allow a greatly increased number of control codes for terminals. The method they arrived at was to select a single ASCII character, which when detected by the terminal, would indicate that the next sequence of characters was a command, not data for display. This simple decision made possible many more than the original 32 control codes for issuing commands to intelligent terminals. You probably guessed that the ASCII character they picked was ASCII 27, commonly known as "escape". All of which brings us back to ANSI.SYS, a subset of the coding language established by the committee. To use it, you must install it as a device driver by adding the following line to the CONFIG.SYS file. DEVICE = ANSI.SYS When listed in the CONFIG.SYS file, ANSI.SYS replaces the CONsole handler that DOS uses by default. Its installation gives you added control over the keyboard and display. Now. As previously mentioned, the leading character of all "control sequences" is ESCape. Unfortunately, it's not possible to enter an ASCII 27 from the keyboard. If you do, DOS simply cancels the current line. But, one of the DOS commands, PROMPT, does allow the sending of <ESC>, as part of a text string, to the console display. It turns out that one of the easiest ways to send commands to ANSI.SYS is by using the PROMPT command. The syntax for PROMPT is: PROMPT [prompt-text] Since the ANSI standard was deliberately designed to be as open-ended as possible, a second leading character is used to define each particular subset. On the IBM PC, that character is the left bracket "[". Therefore each of our control sequences begin with "ESCape [". The characters used by PROMPT to indicate ESCape are "$e", making the beginning of each PROMPT command look like this. PROMPT $e[ ... After these two "lead-in" characters, are the parameters of the ANSI com- mand, then the character that identifies the command. The syntax is: PROMPT $e[<parameter>;...;<parameter><identifier> Cursor Control As an example, let's prepare a command for moving the cursor. There are a total of 10 control sequences that can be used for controlling the cursor, but 2 of them are functionally identical. They are CUP (CUrsor Position) and HVP (Horizontal Vertical Position). We'll use HVP for this example. The syntax we want is: PROMPT $e[<row>;<column>f If you chose to move the cursor to the beginning of the last line of the screen, (row 25, column 1), the command would read: PROMPT $e[25;1f If you type this command and press <enter>, you will see the cursor (a flashing underline) at the beginning of the last line on your screen. The normal DOS drive letter prompt has disappeared. What has happened is that you've changed the standard A> prompt to an abstract prompt which consists of an escape sequence. So every time DOS tries to display the prompt, it is intercepted by ANSI.SYS. It never makes it to the display. If you wish to have your old DOS prompt back, just type the word PROMPT and press <enter>. That causes DOS to revert to the default system prompt. The cursor control sequences may be divided into the following groups. Cursor Movement ------------------------------------------------------- | CUU - CUrsor Up - PROMPT $e[<number of rows>A | | CUD - CUrsor Down - PROMPT $e[<number of rows>B | | CUF - CUrsor Forward - PROMPT $e[<number of columns>C | | CUB - CUrsor Back - PROMPT $e[<number of columns>D | ------------------------------------------------------- Find Current Cursor Position ---------------------------------------------------------- | DSR - Device Status Report - PROMPT $e[6n | | CPR - Cursor Position Report - PROMPT $e[<row>;<column>R | ---------------------------------------------------------- DSR is your query of the device - CPR is the response Cursor Positioning ------------------------------------------------------------------ | CUP - CUrsor Position - PROMPT $e[<row>;<column>H | | HVP - Horizontal & Vertical Position - PROMPT $e[<row>;<column;f | | SCP - Save Cursor Position - PROMPT $e[s | | RCP - Restore Cursor Position - PROMPT $e[u | ------------------------------------------------------------------ Erasing --------------------------------------- | ED - Erase in Display - PROMPT $e[2J | | EL - Erase in Line - PROMPT $e[k | --------------------------------------- With this range of commands at your disposal, you have a lot of power over the curser, enough to build a rudimentary text editor, but the exploration of each is up to you. Mode Control Another feature of ANSI.SYS is the ability to control the mode used for display, including screen width, color, intensity and word wrap. For example, if you wish to set the display to a 40 column screen width using a black and white display attribute, you would use the Set Mode control sequence. Here is the list of possible display modes. Setting the Display Modes --------------------------------------------- | SM - Set Mode - PROMPT $e[=<parameter>h | | RM - Reset Mode - PROMPT $e[=<parameter>l | --------------------------------------------- | parameter list | | ~~~~~~~~~~~~~~ | | 0 - 40x25 black and white |\ | 1 - 40x25 color | \ Text | 2 - 80x25 black and white | / Screens | 3 - 80x25 color |/ | 4 - 320x200 color |\ | 5 - 320x200 black and white | > Graphic | 6 - 640x200 black and white |/ Screens | 7 - if SM, word wrap is on | | if RM, word wrap is off | ----------------------------------- Using the example of a 40 column black and white display, the code sequence would be: PROMPT $e[=0 If you want to change that to a color display with 80 columns, the sequence becomes: PROMPT $e[=3 Now that the console is set for the display of color, a control sequence is needed to set the color and intensity. Setting Color and Intensity ----------------------------------------------------------------------- | SGR - Set Graphics Rendition - PROMPT $e[<parameter>;...;<parameter>m | ----------------------------------------------------------------------- | parameter list | | ~~~~~~~~~~~~~~ | | 0 - normal attributes (default display) | | 1 - bold on (high intensity) | | 4 - underline on (monochrome only) | | 5 - blink on | | 7 - reverse video on | | 8 - canceled on (invisible) | | 30 - black characters | | 31 - red characters | | 32 - green characters | | 33 - yellow characters | | 34 - blue characters | | 35 - magenta characters | | 36 - cyan characters | | 37 - white characters | | 40 - black background | | 41 - red background | | 42 - green background | | 43 - yellow background | | 44 - blue background | | 45 - magenta background | | 46 - cyan background | | 47 - white background | ----------------------------------------------- To set the display to a blue background with red characters displayed in high intensity, the control sequence would be: PROMPT $e[44;31;1m or for blue characters on a light yellow background: PROMPT $e[34;43;7m That is the range of control sequences available for control of the display screen while using ANSI.SYS. Not unlimited to be sure, but it does increase the user's control over the way things are displayed. In fact here is a sample batch file called COLOR.BAT that let's you easily change the color of the characters bring displayed on your screen. The syntax for its use is: COLOR <your choice> COLOR.BAT -------------------------------- | if %1 == red prompt $e[31m | | if %1 == green prompt $e[32m | | if %1 == yellow prompt $e[33m | | if %1 == blue prompt $e[34m | | if %1 == magenta prompt $e[35m | | if %1 == cyan prompt $e[36m | | if %1 == white prompt $e[37m | | prompt | -------------------------------- Redefining the Keyboard One of the most popular types of software on the market allows the user to redefine the keyboard and/or assign strings of characters to single key strokes. What many do not know is that by using the ANSI.SYS device driver these features are already available. If want to rearrange the keyboard to a "davork" layout, (as opposed to qwerty) you can use ANSI.SYS to do it. If you would rather press <Crtl-Home> to clear the screen (like you do while using BASIC) than typing out CLS and pressing <enter>, you can do that too. Or maybe you'd like to spell out the word "Bloomington" by typing <Alt-B>. The keyboard redefinition features of ANSI.SYS are very powerful. Here is the basic control sequence you need for keyboard redefinition. PROMPT $e[<number>;<number>p The 2 numbers stand for, respectively, the ASCII value of the character you want replaced and the ASCII value of the new character. For instance, if you want a "B" to display every time you press "A", the code sequence would be: PROMPT $e[65;66p "A" is ASCII 65 and "B" is ASCII 66. After executing this command, whenever you type "A", you'll see "B" displayed. By building yourself a batch file containing the necessary control sequences, you can use this method to convert your keyboard to the "davork" layout. You can even physically move the keytops if you want. Another form of the control sequence allows a single keystroke to generate a string of characters. It looks like this. PROMPT $e[<number>;"string"p When the command is received, the key that represents the ASCII value of <number> will generate whatever string appears between the two quote marks. For instance, the control sequence, PROMPT $e[122;"zebra"p will cause the "z" key to be replaced by the word "zebra". A more useful feature of key board redefinition is accomplished with yet another form of the control sequence. PROMPT $e[0;<number>;"string";...<number or string>p This is the really powerful version that allows the assigning of strings so that complex commands (or tasks) can be executed using single keystrokes. For instance, I might want to redefine the function keys to perform common DOS commands. The batch file for reassignment might look like this. FKEY-NEW.BAT -------------------------------- | prompt $e[0;59;"dir a:/p";13p | | prompt $e[0;60;"dir b:/p";13p | | prompt $e[0;61;"basica";13p | | prompt $e[0;62;"copy "p | | prompt $e[0;63;"cls";13p | | prompt $e[0;64;"format b:"p | | prompt $e[0;65;"chkdsk "p | | prompt $e[0;66;"mode co80";13p | | prompt $e[0;67;"debug";13p | | prompt $e[0;68;"del "p | | prompt | -------------------------------- Of course, you may prefer to assign different functions to the function keys, so your batch file would have different strings for each key. Notice that in several definitions "13" was added before the identifier "p". That's the ASCII value for carriage return and causes the command to execute automatically when the respective function key is pressed. But there are times when that's not desirable. For example, when using the CHKDSK com- mand, it may be necessary to specify a different drive or include one of the parameters. In such a case, pressing the F7 key displays only "chkdsk" followed by a space. It's up to the user to complete and execute the command. It is possible to assign more than one string to each function key. Since most keys produce a different value (scan code) when pressed in combination with either <shift> key, the <Alt> key or the <Ctrl> key, different strings may be assigned to each combination. That allows 4 strings to be assigned to each function key giving a total of 40 strings just for the function keys. While most may think of only the function keys for string assignment, other possibilities exist. Assignment of string to the standard alpha- numeric keys (letters and numbers) pressed in combination with the <Alt> key is acceptable. This allows us to retain the combination of letter keys and <Ctrl> key for use in imbedding printer control codes in our files, and the original values of the unshifted and shifted keys. If a application program assigns meaning to the function keys, the only remaining choice may be to use the <Alt> key in combination with the alphanumerics for string assign ment. For instance, the control sequence needed to cause the <ALT-d> combination to display the directory of th current drive would be: PROMPT $e[0;32;"dir";13p To make it easier for you to assign strings and/or commands to specific keys, the next page has a table of the numbers (scan codes) for each key that you are likely to want to redefine or assign strings and/or commands to. When you first look at the table, you will notice that there seem to be several codes that are generated by more than one key stroke combination. Not so! All of the function keys (alone or in combination with the <shift>, <Ctrl> and <Alt> keys) and the alphanumeric keys (in combination with the <Alt> key) generate an extended code. Since there are more key stroke combinations than there are ASCII codes, something had to be done to allow the computer to recognize the extra combinations. The solution was to have the addition combinations produce an extended code. These codes consist of two values instead of one. The first value is always a null (ASCII 00) and indicates to the computers CONsole driver that a special key has been pressed. (Remember the leading zero in the above PROMPT string?) The second value is then used to identify the particular key (or combination of keys) that was pressed. Although the codes in the table may at first seem to be duplications, they are not. Hopefully this discussion of ANSI.SYS will help you integrate its use into your computing in order to simplify the execution of routine tasks. by Michael L Hoyt, 5 jul 85 Table of Keyboard Extended Function Codes ----------------------------------------------- | Key Normal <Shift> <Ctrl> <Alt> | | F1 59 84 94 104 | F | F2 60 85 95 105 | U | F3 61 86 96 106 | N K | F4 62 87 97 107 | C E | F5 63 88 98 108 | T Y | F6 64 89 99 109 | I S | F7 65 90 100 110 | O | F8 66 91 101 111 | N | F9 67 92 102 112 | | F10 68 93 103 113 | |===============================================| | 1 49 33 * 120 | | 2 50 64 00 121 | N | 3 51 35 * 122 | U K | 4 52 36 * 123 | M E | 5 53 37 * 124 | B Y | 6 54 94 30 125 | E S | 7 55 38 * 126 | R | 8 56 42 * 127 | | 9 57 40 * 128 | | 0 48 41 * 129 | |===============================================| | A 97 65 01 30 | | B 98 66 02 48 | | C 99 67 03 46 | | D 100 68 04 32 | | E 101 69 05 18 | | F 102 70 06 33 | | G 103 71 07 34 | | H 104 72 08 35 | | I 105 73 09 23 | L | J 106 74 10 36 | E K | K 107 75 11 37 | T E | L 108 76 12 38 | T Y | M 109 77 13 50 | E S | N 110 78 14 49 | R | O 111 79 15 24 | | P 112 80 16 25 | | Q 113 81 17 16 | | R 114 82 18 19 | | S 115 83 19 31 | | T 116 84 20 20 | | U 117 85 21 22 | | V 118 86 22 47 | | W 119 87 23 17 | | X 120 88 24 45 | | Y 121 89 25 21 | | Z 122 90 26 44 | ----------------------------------------------- If *, code is trapped by keyboard routine and not displayed.