Learn to Program with C_ Learn to Program using the Popular C Programming Language ( PDFDrive )

Chapter 7 ■ Functions
int isLowerCase(char ch) {
return ch >= 'a' && ch <= 'z';
} //end isLowerCase
int position(char ch) {
int isUpperCase(char), isLowerCase(char);
if (isUpperCase(ch)) return ch - 'A' + 1;
if (isLowerCase(ch)) return ch - 'a' + 1;
return 0;
} //end isPosition
Here is a sample run of P7.10:
Type some letters and non-letters and press "Enter"
FaT($hY&n
F 6
a 1
T 20
( 0
$ 0
h 8
Y 25
& 0
n 14
We have written the functions isDigit, isUpperCase, isLowerCase, and isLetter to
illustrate basic concepts about character functions. However, C provides a number of predefined
functions (actually, macros, but the distinction is not important for us) for working with
characters. Among these are isdigit (test for a digit), isupper (test for an uppercase letter),
islower (test for a lowercase letter), and isalpha (test for a letter). To use these functions, you
need to place the directive
#include <ctype.h>
at the head of your program. As an exercise, rewrite P7.10 using isupper and islower. Without
isUpperCase, isLowerCase and their prototypes, your program would be much shorter.
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