SECTION C - PRIMER                                   FILE PRIMER.C

                                         VARIABLES
                                         *********

          Variables are one of the features in any computer language which 
          makes it so powerful. We use the term 'VARIABLE' to denote a 
          letter,word or string of characters which represents another letter 
          etc.,or a number.A variable can be just one letter or a combination 
          of letters and numbers but must start with a letter. Letters can be 
          upper or lower case e.g  NAm1 is the same as nAM1,NAM1 or 
          nam1.Otherwise only full stops can be used, and in certain special 
          circumstances ,brackets. A variable may be of any length, but in 
          practice is made as short as possible consistent with clarity. 
          VARIABLE NAMES CANNOT BE IDENTICAL TO BASIC KEYWORDS.
              We have seen before that numbers and letters are sometimes 
          treated differently and this remains the case with variables. a 
          number can be represented by a single letter or string of characters 
          as described above, but a letter or 'string' variable must be 
          followed by the dollar sign $ (SHIFT + 4 key). If a number variable 
          must always represent an integer(whole number) ,it should be 
          followed by the % sign, although for simple programs it can usually 
          be dispensed with. If you are a little bemused, the following 
          listing should make all this clear.
              To change one set of characters for another may not seem very 
          productive, but it is most important,as we shall see. For example we 
          could write at the beginning of a program:  pet$= "dog" .Then every 
          time we should write "dog" we write pet$ instead. Whenever BASIC 
          sees pet$ it will print dog in it's place. If we now change 
          pet$="dog" to pet$="cat", the word "cat" will be substituted for the 
          variable pet$ instead of "dog" at each occurrence. Simply by 
          retyping one word we have changed several. Furthermore BASIC will 
          accomplish this without error 
              Later we shall see how to give values to variables from the 
          keyboard [ Section e ] and how to change variable values with loops 
          [Section d ]. Just for now let us look at the next listing,which 
          demonstrates the points discussed above 
              Do not be afraid to experiment with the listing as described in 
          INTRO.D

          End of file PRIMER.C