SAS/C Library Reference, Vol. 1

isalpha -- Alphabetic Character Test

SYNOPSIS

 #include <ctype.h>

 int isalpha(int c);

DESCRIPTION

isalpha tests an integer value c to determine whether it is an alphabetic (uppercase or lowercase) character. In the C locale, isalpha returns true only for the characters for which isupper or islower is true.

RETURN VALUE

isalpha returns 0 if the character is not alphabetic, or a nonzero value if it is alphabetic. If the argument is EOF, 0 is returned.

CAUTIONS

The effect of isalpha on a noncharacter argument other than EOF is undefined. Do not assume that isalpha returns either 0 or 1.

EXAMPLE

  #include <ctype.h>
  #include <stdio.h>

  #define MAXLEN 40

  main()
  {
     char id[MAXLEN+1];
     int i;
     char *text;
     char input[MAXLEN];

     puts("Enter a string (40 characters maximum). ");
     text = gets(input);

     puts("Initial alphabetic characters you entered:");
     for (i = 0; i < MAXLEN && isalpha(text[i]); i++) {
        id[i] = text[i];
        putc(id[i]);
     }

     id[i] = '0';
     putc('n');
  }

RELATED FUNCTIONS

islower, isupper