ProfitPress Mega CDROM2 …eeware (MSDOS)(1992)(Eng)/ProfitPress-MegaCDROM2.B6I/PROG/PASCAL/PASTUT24.ZIP/PTUTRTXT.ZIP/INTRO.TXT

Text File | 1989-12-01 | 13.2 KB | 296 lines

                                                 INTRODUCTION

IF YOU KNOW NOTHING ABOUT PASCAL
____________________________________________________________

Assuming you know nothing at all about Pascal, and in fact,
that you may know nothing about programming in general, we
will begin to study Pascal.  If you are already somewhat
familiar with programming and especially Pascal, you will
probably want to skip very quickly through the first few
chapters.  You should at least skim these chapters, and you
should read the remainder of this introduction.

A few comments are in order to get us started in the right
direction.  The sample programs included on the disks are
designed to teach you the basics of Pascal and they do not
include any clever or tricky code.  Nearly all of the programs
are really quite dumb as far as being useful programs, but all
will teach one or more principles of Pascal.  I have seen one
tutorial that included a 12 page program as the first example.
In fact there were only 2 example programs in the entire
tutorial, and it was impossible to glean the essentials of
programming from that system.  For this reason, I will
completely bypass any long programs until the very end of this
tutorial.  In order to illustrate fundamental concepts used
in Pascal programming, all programs will be very short and
concise until we reach the last chapter.


LARGER PASCAL PROGRAMS
____________________________________________________________

Chapter 14 has some rather large programs to illustrate to you
how to write a large program.  It would be a disservice to you
to show you all of the constructs of Pascal and not show you
how to put them together in a meaningful way to build a large
program.  After completing all of the fundamentals of Pascal,
it will then be very easy for you to use the tools learned to
build as large a program as you desire or require for your
next programming project.

Another problem I have noticed in example programs is the use
of one word for all definitions.  For example, a sort program
is stored in a file called SORT, the program is named Sort,
and various parts of the program are referred to as Sort1,
Sort2, etc.  This can be confusing since you have no idea if
the program name must be the same as the filename, or if any
of the other names were chosen to be the same because of some
obscure rule not clearly documented.  For this reason, the
example programs use completely arbitrary names whenever the
choice of a name adds nothing to the readability or clarity
of a program.  As an illustration of this, the first program
is named Puppy_Dog.  This adds nothing to the understanding

                                                     Page I-1

                                                 Introduction

of the program but does illustrate that the program name means
nothing to the Pascal compiler concerning what the program
does.

Due to the fundamental design of the Pascal language, certain
words are "reserved" and can only be used for their defined
purposes.  These are listed in your TURBO Pascal reference
manual (page 37 - version 3.0; page 196 - version 4.0;
reference guide page 11 - version 5.x).  All of the sample
programs in this tutorial are written with the reserved words
in all lower-case letters, and the user variables in lower
case with the first letter capitalized since this is becoming
the accepted industry standard.  Don't worry about what
reserved words are yet, they will be completely defined later.

In this tutorial, all reserved words, type names, variable
names, and procedure and function names will be listed in
boldface type within the text as an aid to the student.
Because it would add little and could possibly be confusing,
the simple predefined types will not be listed in boldface
type.


WHAT IS A COMPILER?
____________________________________________________________

There are two methods used to run any computer program that
is written in a readable form of English.  The first method
is to use an interpreter.  An interpreter is a program that
looks at each line of the "English" program, decides what the
"English" on that line means, and does what it says to do.
If one of the lines is executed repeatedly, it must be scanned
and analyzed each time, greatly slowing down the solution of
the problem at hand.  A compiler, on the other hand, is a
program that looks at each statement one time and converts it
into a code that the computer understands directly.  When the
compiled program is actually run, the computer does not have
to figure out what each statement means, it is already in a
form that the computer can run directly, hence a much faster
execution of the program.

This tutorial is written especially for Borland
International's TURBO Pascal compilers version 3.0, 4.0, or
5.x.  These are very high quality compilers that can do nearly
anything you will ask them to do since they are so flexible.
The original intent of this tutorial was to write it in such
a way that it would be completely generic and usable with any
good Pascal compiler.  The programmers at Borland included a
great many nonstandard aids for the Pascal language and
resulted in a very good product that has dominated the market
for microcomputers.  To completely omit all of the extensions
would do those of you with the Borland compiler a real
disservice, and to include the extensions would not allow
other compilers to be used effectively with this tutorial.

                                                     Page I-2

                                                 Introduction


The decision was made to use the Borland extensions and make
the tutorial very difficult to use with other compilers.  If
you have a need to use Pascal with some other compiler, TURBO
Pascal is so inexpensive that it would be a wise decision to
purchase a copy solely for the purpose of learning the Pascal
programming language, then moving to a larger compiler on a
minicomputer or a mainframe using the accumulated knowledge
to very quickly learn the extensions provided by that
particular compiler.  At any rate, this tutorial will not
teach you everything you will ever need to know about Pascal.
It will, however, teach you the fundamentals and the advanced
features of Pascal, but of even more importance is the
definition of Pascal terminology needed to progress on your
own into more advanced topics of Pascal and programming in
general.  You will find that experience will be your best
teacher.


WHICH VERSION OF TURBO PASCAL?
____________________________________________________________

Some of the example files will only work properly with TURBO
Pascal version 3.0 and some will only work properly with
version 4.0 and later, but most will work with either.  It
will be clearly indicated to you which files will work with
any of the versions of TURBO Pascal.  It should be pointed out
that each succesive version of TURBO Pascal has been an
improvement over the previous version since additional
capabilities have been added, and each new one compiles a
little faster and results in smaller but faster executable
code than the previous version.  Any of the versions of TURBO
Pascal can be used to learn to program in Pascal, so whichever
version you have on hand will be adequate.  Later, when you
become more versed in programming techniques, you may wish to
upgrade to the absolute latest version.


WHAT ABOUT TURBO PASCAL VERSION 2.0?
____________________________________________________________

Most of the files will compile properly with TURBO Pascal
version 2.0, but no warning will be given since that version
has been superseded for so long.  It will pay you to purchase
a newer version because of the flexibility.  If you choose not
to however, this tutorial will work fine in most cases if you
follow the instructions for TURBO Pascal version 3.0.


WHAT ABOUT TURBO PASCAL VERSION 5.5?
____________________________________________________________

Chapters 15 and 16 of this tutorial are written especially for
TURBO Pascal version 5.5 to discuss the use of object oriented

                                                     Page I-3

                                                 Introduction

programming and how to use the Borland extensions.  Since the
topic of object oriented programming is a very large and
diverse field of study and only a limited space is available
to discuss it in this tutorial, these chapters will give you
only a brief overview of what it is and how to use it.  You
will find 13 complete example programs to get you started in
this new and very meaningful endeavor and this introduction
should whet your appetite to continue your study in more
depth.


PREPARATION FOR USE OF THIS TUTORIAL.
____________________________________________________________

Copy the example files onto your TURBO working disk and you
are ready to begin, provided of course that you have already
learned how to start the TURBO system and how to edit a Pascal
file.  Be sure you make a backup copy of the Pascal source
disk so you cannot accidentally lose all information on the
distribution disk.  If you are using TURBO Pascal version 3.0,
you should read Chapter 1 of the reference manual to be ready
to use this tutorial, and if you are using TURBO Pascal
version 4.0, you should read parts of chapters 1, 2, & 11 of
your reference manual.  TURBO Pascal version 5.x (5.0 or 5.5)
users should read chapters 1 and 2 of the User's Guide.  You
should be familiar with use of the editor supplied with TURBO
Pascal before beginning.

If you are not using TURBO Pascal, you will still be able to
compile and execute many of these Pascal files, since most of
the examples use standard Pascal syntax.  There will be some
statements used which are unique to TURBO Pascal and will not
work with your compiler.  This will be especially true when
you come to the chapter on standard input and output since
this is where most compilers differ.  Unfortunately, this is
one of the most important aspects of any programming language,
since it is required to get data into and out of the computer
to do anything useful.  You will also find that chapter 13,
covering the topic of units, is unique to TURBO Pascal and
will not work with any Pascal compilers other than TURBO
Pascal versions 4.0 and 5.x.


WHAT ABOUT THE PROGRAMMING EXERCISES?
____________________________________________________________

It is highly suggested that you do the programming exercises
after you complete the study for each chapter.  They are
carefully selected to test your understanding of the material
covered in that chapter.  If you do not write, enter, debug,
and run these programs, you will only be proficient at reading
Pascal.  If you do the exercises completely, you will have a
good start at being a Pascal program writer.


                                                     Page I-4

                                                 Introduction

It should also be mentioned that this tutorial will not teach
you everything you will ever need to know about Pascal.  You
will continue to learn new techniques as long as you continue
to write programs.  Experience is the best teacher here just
as it is in any endeavor.  This tutorial will teach you enough
about Pascal that you should feel very comfortable as you
search through the reference manual for some topic.  You will
also be able to read and understand any Pascal program you
find in textbooks or magazines.  Although the primary goal of
this tutorial is to teach you the syntax and use of Pascal,
the most important byproduct is the knowledge of Pascal
terminology you will gain.  This terminology will enable you
to learn even more about Pascal and programming in general.


THE ANSWERS DIRECTORY
____________________________________________________________

There is a directory on the distribution disk named ANSWERS
which contains an answer to each of the programming exercises
given at the end of the chapters.  You should attempt to do
original work on each of the exercises before referring to
these answers, in order to gain your own programming
experience.  These answers are given for your information in
case you are completely stuck on how to solve a particular
problem.  These answers are not meant to be the only answer,
since there are many ways to program anything, but they are
meant to illustrate one way to solve the suggested programming
problem.

The answers are all in executable files named in the format
CHnn_m.PAS where nn is the chapter number, and m is the
exercise number.  If there is more than one answer required,
an A, B, or C is included following the exercise number.


A SPECIAL NOTE FOR THE SHAREWARE VERSION
____________________________________________________________

It is impossible to include the graphics diagrams in chapter
12 in a pure ASCII text.  They are therefore omitted from this
version of the tutorial.  If you need these diagrams, they can
be purchased directly from Coronado Enterprises along with
your registration.  See the READ.ME file on either diskette
for more information.










                                                     Page I-5