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INTRO.TXT
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1988-11-27
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Introduction to the TURBO Pascal Tutorial
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 the first few
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. I will completely
bypass any long programs until the very end of this tutorial
in order to illustrate concepts used in Pascal programming.
It will then be very easy for you to use the tools learned
to build as large a program as you desire.
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 on page 37 of the TURBO
PASCAL manual (version 3.0 will be used in all references).
All of the sample programs are written with the reserved
words in all capital letters, and the user variables in
lower case. Don't worry about what reserved words are yet,
they will be completely defined later.
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.
What is a compiler? There are two primary methods used
in running any computer program that is written in a
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Introduction to the TURBO Pascal Tutorial
readable form of English. The first method is 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.
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 tutorial disks so you cannot accidentally lose all
information on the distribution disks. You should read
Chapter 1 of the TURBO Pascal reference manual to be ready
to use this tutorial. 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 most of these Pascal files,
since most of the examples use "standard" Pascal. There
will be some statements used which are unique to TURBO
Pascal and will probably 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.
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 each 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
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Introduction to the TURBO Pascal Tutorial
teacher here just as it is in any endeavor. This tutorial
will teach you enough about Pascal that you will 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.
When you are ready, I will meet you in Chapter 1.
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