Ctutor chapter 13

                 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_line".   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.

                        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.   There  are

        several  others that are commonly used,  so they are defined

        in the following table;

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

             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

        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?



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                 Chapter 13 - Character and Bit Manipulation



             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

        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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