C/C++ Users Group Library 1996 July/C-C++ Users Group Library July 1996.iso/vol_300/353_01/intro.txt

Text File | 1992-01-18 | 12KB | 294 lines

                                                     Introduction
                                                      WHAT IS C++


THE ORIGIN OF C++
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The C programming language was developed at AT&T for the purpose
of writing the operating system for the PDP-11 series of computers
which ultimately became the unix operating system.  C was developed
with the primary goal of operating efficiency.  Bjarne Stroustrup,
also of AT&T, developed C++ in order to add object oriented
constructs to the C language.  Because object oriented technology
was new at the time and all existing implementations of object
oriented languages were very slow and inefficient, the primary goal
of C++ was to maintain the efficiency of C.

C++ can be viewed as a procedural language with some additional
constructs, some of which are added for object oriented programming
and some for improved procedural syntax.  A well written C++
program will reflect elements of both object oriented programming
style and classic procedural programming.  C++ is actually an
extendible language since we can define new types in such a way
that they act just like the predefined types which are part of the
standard language.  C++ is designed for large scale software
development.



HOW TO GET STARTED IN C++
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The C programming language was originally defined by the classic
text authored by Kernigan and Ritchie, "The C Programming
language", and was the standard used by all C programmers until a
few years ago.  The ANSI standard for C was finally approved in
December of 1989 and has become the official standard for
programming in C.  Since the ANSI standard adds many things to the
language which were not a part of the Kernigan and Ritchie
definition, and changes a few, the two definitions are not
absolutely compatible and some experienced C programmers may not
have studied the newer constructs added to the language by the
ANSI-C standard.


This tutorial will assume a thorough knowledge of the C programming
language and little time will be spent on the fundamental aspects
of the language.  However, because we realize that many programmers
have learned the dialect of C as defined by Kernigan & Ritchie,
some sections will be devoted to explaining the newer additions as

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                                       Introduction - What is C++

provided by the ANSI-C standard.  As the ANSI-C standard was in
development, many of the newer constructs from C++ were included
as parts of C itself, so even though C++ is a derivation and
extension of C, it would be fair to say that ANSI-C has some of its
roots in C++.  An example is prototyping which was developed for
C++ and later added to C.

The best way to learn C++ is by using it.  Almost any valid C
program is also a valid C++ program, and in fact the addition of
about 12 keywords is the only reason that some C programs will not
compile and execute as a C++ program.  There are a few other subtle
differences but we will save the discussion of them until later.
Since this is true, the best way to learn C++ is to simply add to
your present knowledge and use a few new constructs as you need
them for each new program.  It would be a tremendous mistake to try
to use all of the new constructs in your first C++ program.  You
would probably end up with an incomprehensive mixture of code that
would be more inefficient than the same program written purely in
C.  It would be far better to add a few new constructs to your
toolkit each day, and use them as needed while you gain experience
with their use.

As an illustration of the portability of C to C++, all of the
example programs included in the Coronado Enterprises C tutorial
compile and execute correctly when compiled as C++ programs with
no changes.  None of the C++ programs will compile and execute
correctly with any C compiler however, if for no other reason than
the use of the new style of C++ comments.



HOW TO USE THIS TUTORIAL
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This tutorial is best used while sitting in front of your computer.
It is designed to help you gain experience with your own C++
compiler in addition to teaching you the proper use of C++.
Display an example program on the monitor, using whatever text
editor you usually use, and read the accompanying text which will
describe each new construct introduced in the example program.
After you study the program, and understand the new constructs,
compile and execute the program with your C++ compiler.

After you successfully compile and execute the example program,
introduce a few errors into the program to see what kind of error
messages are issued.  If you have done much programming, you will
not be surprised if your compiler gives you an error message that
seems to have nothing to do with the error introduced.  This is
because error message analysis is a very difficult problem with any
modern programming language.  The most important result of these
error introduction exercises is the experience you will gain using
your compiler and understanding its nuances.  You should then
attempt to extend the program using the techniques introduced with
the program to gain experience.

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                                       Introduction - What is C++


In the text of this tutorial, keywords, variable names, and
function names will be written in bold type as an aid when you are
studying the example programs.

The way this tutorial is written, you will not find it necessary
to compile and execute every program.  At the end of each example
program, listed in comments, you will find the result of execution
of that program.  Some of the constructs are simple and easy for
you to understand, so you may choose to ignore compilation and
execution of that example program, depending upon the result of
execution to give you the output.  Some students have used these
results of execution to study several chapters of this tutorial on
an airplane by referring to a hardcopy of the example programs.


DIFFERENT C++ IMPLEMENTATIONS
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There are primarily two standards for naming C++ files, one using
the extension CPP and the other using the extension CXX.  All files
in this tutorial use the CPP extension for naming files.  If your
compiler requires the CXX extension it will be up to you to rename
the files.  When C++ was in its infancy, header files generally
used the extension .HPP, but there is a definite trend to use .H
for all header files.  For that reason all header files in this
tutorial will use that convention.

Even though we have tried to use the most generic form of all
constructs, it is possible that some constructs will not actually
compile and run with some C++ compilers.  As we find new
implementations of C++, and acquire copies of them, we will compile
and execute all files in an attempt to make all example programs
as universal as possible.

The C++ language is very new and is changing rapidly.  The
developer of the language, AT&T, has changed the formal definition
several times in the last few years and the compiler writers are
staying busy trying to keep up with them.  It would be best for you
to search the more popular programming languages for evaluations
and comparisons of compilers.  New C++ implementations are being
introduced at such a rapid rate, that we cannot make a compiler
recommendation here.


PRINTING OUT THE EXAMPLE PROGRAMS
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Some students prefer to work from a hardcopy of the example
programs.  If you desire to print out the example programs, there
is a batch file on the distribution disk to help you do this.  Make
the distribution disk the defaul