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CHAP13.TXT
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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 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 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 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
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 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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Chapter 13 - Character and Bit Manipulation
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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