The function definition of isalnum()
is:
int isalnum(int argument);
It is defined in the ctype.h header file.
isalnum() Parameters
- argument - a character
isalnum() Return Value
- Returns 1 if argument is an alphanumeric character.
- Returns 0 if argument is neither an alphabet nor a digit.
Example #1: isalnum() function return value
#include <stdio.h>
#include <ctype.h>
int main()
{
char c;
int result;
c = '5';
result = isalnum(c);
printf("When %c is passed, return value is %d\n", c, result);
c = 'Q';
result = isalnum(c);
printf("When %c is passed, return value is %d\n", c, result);
c = 'l';
result = isalnum(c);
printf("When %c is passed, return value is %d\n", c, result);
c = '+';
result = isalnum(c);
printf("When %c is passed, return value is %d\n", c, result);
return 0;
}
Output
When 5 is passed, return value is 1 When Q is passed, return value is 1 When l is passed, return value is 1 When + is passed, return value is 0
Example #2: Check if a character is an alphanumeric character
#include <stdio.h>
#include <ctype.h>
int main()
{
char c;
printf("Enter a character: ");
scanf("%c", &c);
if (isalnum(c) == 0)
printf("%c is not an alphanumeric character.", c);
else
printf("%c is an alphanumeric character.", c);
return 0;
}
Output
Enter a character: 0 0 is an alphanumeric character.