


                                                        Chapter 1
                                                  GETTING STARTED

WHAT IS AN IDENTIFIER
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Before you can do anything in any language, you must at least 
know how to name an identifier.  An identifier is used for any 
variable, function, data definition, etc.  In the programming 
language C, an identifier is a combination of alphanumeric 
characters, the first being a letter of the alphabet or an 
underline, and the remaining being any letter of the alphabet, 
any numeric digit, or the underline.  In the case of some 
compilers, a dollar sign is permitted but not as the first 
character of an identifier.  It should be pointed out that even 
though a dollar sign may be permitted by your C compiler, it is 
not used anywhere in this tutorial since it is not in general 
use by C programmers, and is not even allowed by most compilers.  
If you do not plan to write any portable code, you can use it at 
will if you feel it makes your code more readable.

Two rules must be kept in mind when naming identifiers.

1.   The case of alphabetic characters is significant.  Using 
     INDEX for a variable name is not the same as using index and 
     neither of them is the same as using InDeX for a variable 
     name.  All three refer to different variables.

2.   According to the ANSI-C standard, at least 31 significant 
     characters can be used and will be considered significant by 
     a conforming ANSI-C compiler.  If more than 31 are used, 
     they may be ignored by any given compiler.  


WHAT ABOUT THE UNDERLINE?
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Even though the underline can be used as part of a variable name, 
and adds greatly to the readability of the resulting code, it 
seems to be used very little by experienced C programmers.  A few 
underlines are used for illustration in this tutorial.  Since 
most compiler writers use the underline as the first character 
for variable names internal to the system, you should refrain 
from using the underline to begin a variable to avoid the possi-
bility of a name clash.  To get specific, identifiers with two 
leading underscores are reserved for the compiler as well as 
identifiers beginning with a single underscore and using an upper 
case alphabetic character for the second.  If you make it a point 
of style to never use an identifier with a leading underline, you 
will never have a naming clash with the system.

It adds greatly to the readability of a program to use descrip-
tive names for variables and it would be to your advantage to do 


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                                      Chapter 1 - Getting Started

so.  Pascal programmers tend to use long descriptive names, but 
most C programmers tend to use short cryptic names.  Most of the 
example programs in this tutorial use very short names for that 
reason, but a few longer names are used for illustrative purposes.


KEYWORDS
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There are 32 words defined as keywords in C.  These have prede-
fined uses and cannot be used for any other purpose in a C 
program.  They are used by the compiler as an aid to compiling 
the program.  They are always written in lower case.  A complete 
list follows;

     auto          double        int           struct
     break         else          long          switch
     case          enum          register      typedef
     char          extern        return        union
     const         float         short         unsigned
     continue      for           signed        void
     default       goto          sizeof        volatile
     do            if            static        while

In addition to this list of keywords, your compiler may define a 
few more.  If it does, they will be listed in the documentation 
that came with your compiler.  Each of the above keywords will be 
defined, illustrated, and used in this tutorial. 


WE NEED DATA AND A PROGRAM
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Any computer program has two entities to consider, the data, and 
the program.  They are highly dependent on one another and care-
ful planning of both will lead to a well planned and well written 
program.  Unfortunately, it is not possible to study either 
completely without a good working knowledge of the other.  For 
that reason, this tutorial will jump back and forth between 
teaching methods of program writing and methods of data 
definition.   Simply follow along and you will have a good under-
standing of both.  Keep in mind that, even though it seems 
expedient to sometimes jump right into coding the program, time 
spent planning the data structures will be well spent and the 
quality of the final program will reflect the original planning.


HOW THIS TUTORIAL IS WRITTEN
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As you go through the example programs, you will find that every 
program is complete.  There are no program fragments that could 
be confusing.  This allows you to see every requirement that is 
needed to use any of the features of C as they are presented.  
Some tutorials I have seen give very few, and very complex 
examples.  They really serve more to confuse the student.  This 

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                                      Chapter 1 - Getting Started

tutorial is the complete opposite because it strives to cover 
each new aspect of programming in as simple a context as possible.  
This method, however, leads to a lack of knowledge in how the 
various parts are combined.  For that reason, the last chapter is 
devoted entirely to using the features taught in the earlier 
chapters.  It will illustrate how to put the various features 
together to create a usable program.  They are given for your 
study, and are not completely explained.  Enough details of their 
operation are given to allow you to understand how they work 
after you have completed all of the previous lessons.

Throughout this tutorial, keywords, variable names, and function 
names will be given in boldface as an aid to the student.  These 
terms will be completely defined throughout the tutorial.


RESULT OF EXECUTION
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The result of executing each program will be given in comments at 
the end of the program listing, after the comment is defined in 
about the fourth program of chapter 2.  If you feel confident 
that you completely understand the program, you can simply refer 
to the result of execution to see if you understand the result.  
In this case, it will not be necessary for you to compile and 
execute every program.  It would be a good exercise for you to 
compile and execute some of them however, because all C compilers 
will not generate exactly the same results and you need to get 
familiar with your own compiler.

At this point, you should load and run          =================
FIRSTEX.C if you have not yet done so, to           FIRSTEX.C
see that your C compiler is properly loaded     =================
and operating.  Don't worry about what the 
program does yet.  In due time you will understand it completely.

Note that this program may give you a warning that printf() is 
undefined.  Whether or not you get the warning depends on your 
compiler and how it is set up.  At this point, you can completely 
ignore this warning.  We will cover the reason for the warning 
later in this tutorial.


A WORD ABOUT COMPILERS
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All of the example programs in this tutorial will compile and 
execute correctly with any good ANSI compatible C compiler.  Some 
compilers have gotten extremely complex and hard to use for a 
beginning C programmer, and some only compile and build MS 
Windows programs.  Fortunately, most of the C compilers available 
have a means of compiling a standard C program which is written 
for the DOS environment.  You should check your documentation for 
the capabilities and limitations of your compiler.  If you have 


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                                      Chapter 1 - Getting Started

not yet purchased a C compiler, you should find one that is 
ANSI-C compliant, and that generates a DOS executable.


A DISCUSSION OF SOME OF THE FILES
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LIST.EXE

This file will list the source files on your printer for 
you with the filename and line numbers.  To use it, simply type 
LIST followed by the appropriate filename.  At the user prompt, 
enter the command LIST FIRSTEX.C now for an example.  C source 
code is given in Chapter 14 for this program along with a brief 
description of its operation.  After you have completed your 
study of C, you will have the ability to read and understand the 
source code for this program.


PRINTALL.BAT

This is a batch file that will call the above LIST.EXE file once 
for each of the example C programs, printing all of the files out.  
If you want a hardcopy of all of the files, enter the command 
PRINTALL at the user prompt and watch as your printer fills about 
100 sheets of paper with C programs. 


THE \ANSWERS DIRECTORY
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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.C where nn is the chapter number, and m is the exercise 
number.  If more than one answer is required, an A, B, or C is 
included following the exercise number.










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