CD Actual 15/CDACTUAL15.iso/cdactual/program/pascal/PAS_TUT.ZIP/INTRO.TXT

Text File | 1991-02-04 | 13.4 KB | 295 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 16 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 of the program but does illustrate that the program
name means nothing to the Pascal compiler concerning what the
program does.

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                                                     Introduction

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.  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 possible 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,
resulting in a much faster execution of the program.

This tutorial is written especially for Borland International's
TURBO Pascal compilers version 5.0 through 6.0.  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.

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


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                                                     Introduction

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 programs will not work with some of the earlier
versions of TURBO Pascal.  This is primarily due to fact that
object oriented programming capabilities were added to version 5.5,
and improved on in version 6.0.  Most of the example programs will
work with any version however.  It should be pointed out that each
successive 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.


EARLY VERSIONS OF TURBO PASCAL
_________________________________________________________________

Most of the files will compile properly with TURBO Pascal versions
2.0 through 4.0.  No warning will be given about which files will
not compile with these versions since they have been superseded for
so long.  If you are still using one of the earlier versions, it
would you to purchase a newer version because of the flexibility.


WHAT ABOUT TURBO PASCAL VERSION 5.5 & 6.0?
_________________________________________________________________

Chapters 14 and 15 of this tutorial are written especially for
TURBO Pascal version 5.5 and 6.0 to discuss the use of object
oriented 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.

If you are using an early version of TURBO Pascal without the
object oriented extensions, it would pay you to upgrade to learn
how to use this new programming method.  Object oriented

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                                                     Introduction

programming has the potential to greatly improve the quality of
your code and to reduce the debugging time required.


PREPARATION FOR USE OF THIS TUTORIAL.
_________________________________________________________________

Copy the example files into your TURBO Pascal working directory 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.  TURBO Pascal version 5.x (5.0 or 5.5) users should read
chapters 1 and 2 of the User's Guide, while version 6.0 users
should read chapter 1 and quickly browse through chapters 7 and 8
of the User's Guide.  You should be familiar with the 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.



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.

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

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                                                     Introduction

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.





















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