The isalnum() function in C use to checks given argument  is an alphanumeric character (alphabet or number) or not.

Syntax : -

int isalnum(int argument);

This function is define in ctype.h header file.

Return Value For isalnum() function in c

it return 1 if given argument in program is an alphanumeric character.

isalnum() function return 0 if given argument in program is not an alphabet or a digit.

Example program for isalnum() function in c

#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 of Program

• 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