Chapter 13 - Character and Bit Manipulation


                            UPPER AND LOWER CASE

             Load  and display the program UPLOW.C for an example of
        a  program that does lots of character  manipulation.   More
        specifically,  it changes the case of alphabetic  characters
        around.   It illustrates the use of four functions that have
        to  do with case.   It should be no problem for you to study
        this program on your own and understand how it  works.   The
        four functions on display in this program are all within the
        user written function, "mix_up_the_chars".  Compile and  run
        the  program  with  the  file  of  your  choice.   The  four
        functions are;

             isupper();     Is the character upper case?
             islower();     Is the character lower case?
             toupper();     Make the character upper case.
             tolower();     Make the character lower case.

             Many  more Classification and Conversion  routines  are
        listed on pages 10 and 11 of your Turbo C Reference Guide.

                        CLASSIFICATION OF CHARACTERS

             Load  and display the next program, CHARCLAS.C  for  an
        example of character counting.  We have repeatedly used  the
        backslash  n character representing a new line.   These  are
        called escape sequences, and some of the more commonly  used
        are defined in the following table;

             \n             Newline
             \t             Tab
             \b             Backspace
             \"             Double quote
             \\             Backslash
             \0             NULL (zero)

             A complete list of escape sequences available with your
        Turbo  C  compiler are listed on page 201 of  your  Turbo  C
        Reference Manual.

             By  preceding  each of the above  characters  with  the
        backslash character, the character can be included in a line
        of text for display,  or printing.   In the same way that it
        is  perfectly  all right to use the letter "n" in a line  of
        text as a part of someone's name, and as an end-of-line, the
        other  characters can be used as parts of text or for  their
        particular functions.

             The program on your screen uses the functions that  can
        determine   the  class  of  a  character,   and  counts  the
        characters  in  each class.   The number of  each  class  is


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                 Chapter 13 - Character and Bit Manipulation


        displayed  along with the line itself.   The three functions
        are as follows;

             isalpha();     Is the character alphabetic?
             isdigit();     Is the character a numeral?
             isspace();     Is the character any of, \n, \t,
                              or blank?

             As  noted above, many more Classification Routines  are
        listed on page 10 of your Turbo C Reference Guide.

             This program should be simple for you to find your  way
        through  so no explanation will be given.   It was necessary
        to give an example with these functions used.   Compile  and
        run this program with any file you choose.

                           THE LOGICAL FUNCTIONS

             Load and display the program BITOPS.C. The functions in
        this  group of functions are used to do bitwise  operations,
        meaning  that  the operations are performed on the  bits  as
        though they were individual bits.   No carry from bit to bit
        is performed as would be done with a binary addition.   Even
        though  the operations are performed on a single bit  basis,
        an entire byte or integer variable can be operated on in one
        instruction.   The operators and the operations they perform
        are given in the following table;

             &    Logical AND, if both bits are 1, the result is 1.
             |    Logical OR, if either bit is one, the result is 1.
             ^    Logical XOR,  (exclusive OR),  if one and only one
                    bit is 1, the result is 1.
             ~    Logical invert,  if the bit is 1, the result is 0,
                    and if the bit is 0, the result is 1.

             The  example  program  uses  several  fields  that  are
        combined  in each of the ways given above.   The data is  in
        hexadecimal  format.   It  will be assumed that you  already
        know hexadecimal format if you need to use these operations.
        If  you  don't,  you  will need to study  it  on  your  own.
        Teaching  the  hexadecimal format of numbers is  beyond  the
        scope of this tutorial.

             Run the program and observe the output.

                           THE SHIFT INSTRUCTIONS

             The  last two operations to be covered in this  chapter
        are  the left shift and the right shift instructions.   Load
        the example program SHIFTER.C for an example using these two



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        instructions.    The   two  operations  use  the   following
        operators;

             << n      Left shift n places.
             >> n      Right shift n places.

             Once again the operations are carried out and displayed
        using the hexadecimal format.   The program should be simple
        for you to understand on your own, there is no tricky code.












































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