C/C++ Interactive Guide/c-cplusplus-interactive-guide.iso/c_ref/csource4/252_01/intro.txt

Text File | 1990-02-15 | 9KB | 234 lines

                               Introduction to the C Tutorial



C IS USUALLY FIRST
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The programming language C was originally developed by Dennis
Ritchie of Bell Laboratories and was designed to run on a
PDP-11 with a UNIX operating system.  Although it was
originally intended to run under UNIX, there has been a great
interest in running it under the MS-DOS operating system on
the IBM PC and compatibles.  It is an excellent language for
this environment because of the simplicity of expression, the
compactness of the code, and the wide range of applicability.
Also, due to the simplicity and ease of writing a C compiler,
it is usually the first high level language available on any
new computer, including microcomputers, minicomputers, and
mainframes.

C is not a good beginning language because it is somewhat
cryptic in nature.  It allows the programmer a wide range of
operations from high level down to a very low level,
approaching the level of assembly language.  There seems to
be no limit to the flexibility available.  One experienced C
programmer made the statement, "You can program anything in
C", and the statement is well supported by my own experience
with the language.  Along with the resulting freedom however,
you take on a great deal of responsibility because it is very
easy to write a program that destroys itself due to the silly
little errors that a good Pascal compiler will flag and call
a fatal error.  In C, you are very much on your own as you
will soon find.



I ASSUME YOU KNOW A LITTLE PROGRAMMING
____________________________________________________________

Since C is not a beginners language, I will assume you are not
a beginning programmer, and I will not attempt to bore you by
defining a constant and a variable.  You will be expected to
know these basic concepts.  You will, however, be expected to
know nothing of the C programming language.  I will begin with
the most basic concepts of C and take you up to the highest
level of C programming including the usually intimidating
concepts of pointers, structures, and dynamic allocation.  To
fully understand these concepts, it will take a good bit of
time and work on your part because they not particularly easy
to grasp, but they are very powerful tools.  Enough said about
that, you will see their power when we get there, just don't
allow yourself to worry about them yet.

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                               Introduction to the C Tutorial

Programming in C is a tremendous asset in those areas where
you may want to use Assembly Language but would rather keep
it a "simple to write" and "easy to maintain" program.  It has
been said that a program written in C will pay a premium of
a 20 to 50% increase in runtime because no high level language
is as compact or as fast as Assembly Language.  However, the
time saved in coding can be tremendous, making it the most
desirable language for many programming chores.  In addition,
since most programs spend 90 percent of their operating time
in only 10 percent or less of the code, it is possible to
write a program in C, then rewrite a small portion of the code
in Assembly Language and approach the execution speed of the
same program if it were written entirely in Assembly Language.

Even though the C language enjoys a good record when programs
are transported from one implementation to another, there are
differences in compilers as you will find anytime you try to
use another compiler.  Most of the differences become apparent
when you use nonstandard extensions such as calls to the DOS
BIOS when using MS-DOS, but even these differences can be
minimized by careful choice of programming means.

Throughout this tutorial, every attempt will be made to
indicate to you what constructs are available in every C
compiler because they are part of the accepted standard of
programming practice.



WHAT IS THE ANSI-C STANDARD?
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When it became evident that the C programming language was
becoming a very popular programming language available on a
wide range of computers, a group of concerned individuals met
to propose a standard set of rules for the use of the C
programming language.  The group represented all sectors of
the software industry and after many meetings, and many
preliminary drafts, they finally wrote an acceptable standard
for the C language.  By the time you read this, it should be
accepted by the American National Standards Institute (ANSI),
and by the International Standards Organization (ISO).  It is
not forced upon any group or user, but since it is so widely
accepted, it would be economical suicide for any compiler
writer to refuse to conform to the standard.



YOU MAY NEED A LITTLE HELP
____________________________________________________________

Modern C compilers are very capable systems, but due to the
tremendous versatility of a C compiler, it could be very
difficult for you to learn how to use it effectively.  If you

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                               Introduction to the C Tutorial

are a complete novice to programming, you will probably find
the installation instructions somewhat confusing.  You may be
able to find a colleague or friend that is knowledgeable about
computers to aid you in setting up your compiler for use.

This tutorial cannot cover all aspects of programming in C,
simply because there is too much to cover, but it will
instruct you in all you need for the majority of your
programming in C.  You will receive instruction in all of the
programming constructs in C, but what must be omitted are
methods of programming since these can only be learned by
experience.  More importantly, it will teach you the
vocabulary of C so that you can go on to more advanced
techniques using the programming language C.  A diligent
effort on your part to study the material presented in this
tutorial will result in a solid base of knowledge of the C
programming language.  You will then be able to intelligently
read technical articles or other textbooks on C and greatly
expand your knowledge of this modern and very popular
programming language.



HOW TO USE THIS TUTORIAL
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This tutorial is written in such a way that the student should
sit before his computer and study each example program by
displaying it on the monitor and reading the text which
corresponds to that program.  Following his study of each
program, he should then compile and execute it and observe the
results of execution with his compiler.  This enables the
student to gain experience using his compiler while he is
learning the C programming language.  It is strongly
recommended that the student study each example program in the
given sequence then write the programs suggested at the end
of each chapter in order to gain experience in writing C
programs.



THIS IS WRITTEN PRIMARILY FOR MS-DOS
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This tutorial is written primarily for use on an IBM-PC or
compatible computer but can be used with any ANSI standard
compiler since it conforms so closely to the ANSI standard.
In fact, a computer is not even required to study this
material since the result of execution of each example program
is given in comments at the end of each program.





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                               Introduction to the C Tutorial

RECOMMENDED READING AND REFERENCE MATERIAL
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"The C Programming Language - Second Edition",
Brian W. Kernigan & Dennis M. Ritchie, Prentiss-Hall, 1988

This is the definitive text of the C programming language
and is required reading for every serious C programmer.
Although the first edition was