isalnum Function

Test for an alphanumeric character.

Include

<ctype.h>

Prototype

int isalnum(int c);

Argument

c

The character to test.

Return Value

Returns a non-zero integer value if the character, c, is alphanumeric; otherwise, returns a zero.

Remarks

Alphanumeric characters are included within the ranges A-Z, a-z or 0-9.

Example

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

int main(void)
{
  int ch;

  ch = '3';
  if (isalnum(ch))
    printf("3 is an alphanumeric\n");
  else
    printf("3 is NOT an alphanumeric\n");
 
  ch = '#';
  if (isalnum(ch))
    printf("# is an alphanumeric\n");
  else
    printf("# is NOT an alphanumeric\n");
}

Example Output

3 is an alphanumeric
# is NOT an alphanumeric