C Tutor chapter 1

                        Chapter 1 - Getting Started


                          WHAT IS AN IDENTIFIER?

             Before you can do anything in any language, you must at

        least  know  how you 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.  Two

        rules must be kept in mind when naming identifiers.

        1.   The  case  of  alphabetic  characters  is  significant. 

             Using  "INDEX" for a variable is not the same as  using

             "index"  and  neither  of them is  the  same  as  using

             "InDeX"  for a variable.   All three refer to different

             variables.

        2.   As C is defined, up to eight significant characters can

             be  used and will be considered significant.   If  more     

             than  eight  are  used,  they may  be  ignored  by  the     

             compiler.   This  may  or  may  not  be  true  of  your

             compiler.  You  should  check your reference manual  to

             find  out how many characters are significant for  your

             compiler.

             It  should be pointed out that some C  compilers  allow

        use of a dollar sign in an identifier name,  but since it is

        not  universal,  it  will  not  be  used  anywhere  in  this

        tutorial.    Check  your  documentation  to  see  if  it  is

        permissible for your particular compiler.

                         WHAT ABOUT THE UNDERLINE?

             Even  though  the  underline can be used as part  of  a

        variable  name,   it  seems  to  be  used  very  little   by

        experienced   C  programmers.    It  adds  greatly  to   the

        readability  of  a  program  to use  descriptive  names  for

        variables  and  it  would be to your  advantage  to  do  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.

             Any computer program has two entities to consider,  the

        data,  and  the program.   They are highly dependent on  one

        another  and  careful 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 this reason, this tutorial will

        jump  back  and forth between teaching  methods  of  program

        writing  and  methods of data  definition.    Simply  follow



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                        Chapter 1 - Getting Started


        along and you will have a good understanding of both.   Keep

        in  mind that,  even though it seems expedient to  sometimes

        jump right into the program coding,  time spent planning the

        data  structures  will be well spent and the  final  program

        will reflect the original planning.

                        HOW THIS TUTORIAL IS WRITTEN

             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 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.

                     A DISCUSSION OF SOME OF THE FILES

                                   CCL.BAT

             This  file,  which  does not exist on the  distribution

        disk,  is the batch file that calls in an editor,  then  the

        compiler (Pass 1 and Pass 2, if it exists), and finally runs

        the resulting compiled program.   There are several examples

        of  batch  files  which can be used with  various  compilers

        given  in  the  "COMPILER.DOC"  file  on  the   distribution

        diskette.   It  is up to you to type in a batch file for use

        with your particular compiler,  considering also the  method

        required to call in your editor.  To use it, simply type the

        batchfile  name with the desired filename.   After typing in

        your particular CCL.BAT file,  try it by typing CCL FIRSTEX. 

        You  will  get the source file displayed on the  monitor  by

        your editor.   If you don't have one of the compilers listed

        in  the  "COMPILER.DOC" file,  you will have to  modify  the

        batch file for your particular compiler.
       
             The  pass or passes of the compiler will  be  executed,

        followed by the linking process.   The final program will be

        loaded and run, then the files generated by the process will

        be erased to prevent filling the disk up.



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                        Chapter 1 - Getting Started



             If you have a hard disk available, it will be up to you

        to  modify  the  batch file to perform the  above  described

        operations.

             Even though you will have a lot of files to compile and

        run, you will find that a batch file similar to this will do

        most of the work for you and you will proceed very quickly.

             In order to do the programming exercises, you will need

        to  go  through the same steps as when running  the  example

        programs.   This  is simple to do by simply typing your  own

        filename   with  the  CCL  program  call.    It  is   highly

        recommended  that you do the programming exercises  to  gain

        the programming experience.

                                  LIST.EXE

             This  file will list the source files for you with line

        numbers  and  filename.   To  use  it,  simply  type  "LIST"

        followed by the appropriate filename.   Type LIST  FIRSTEX.C

        now  for  an example.   The C source code is given later  in

        Chapter 14 along with a brief description of its operation.

                                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 PRINTALL and watch as your printer fills about

        150 sheets of paper with C programs.






















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