Shareware Overload/ShartewareOverload.cdr/progm/ctutor1.zip/CHAP13.TXT

Text File | 1989-11-10 | 5KB | 176 lines

                                                   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             UPLOW.C
character manipulation.  More specifically,     =============
it changes the case of alphabetic characters.
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(c);     Is the character upper case?
     islower(c);     Is the character lower case?
     toupper(c);     Make the character upper case.
     tolower(c);     Make the character lower case.

Many more classification and conversion routines should be
listed in the reference material for your compiler.



CLASSIFICATION OF CHARACTERS
____________________________________________________________

Load and display the next program, CHARCLAS.C  ==============
for an example of character counting.  We        CHARCLAS.C
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)

Consult your compiler documentation for a complete list of
escape sequences available with your compiler.

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

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                  Chapter 13 - Character and Bit Manipulation

someone's name, and as an end-of-line, the other characters
can be used as parts of text or for their particular
functions.

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

As noted above, many more classification routines are
available with your compiler.

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     BITOPS.C
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.  Be sure to compile and execute this program and
observe the output.



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                  Chapter 13 - Character and Bit Manipulation

THE SHIFT INSTRUCTIONS
____________________________________________________________

The last two operations to be covered in this   =============
chapter are the left shift and the right          SHIFTER.C
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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