#include <stdio.h> int is_hex_digit(char input) { if((input>='0'&&input<='9')||(input>='a'&&input<='z')||(input>='A'&&input<='F')) { return 1; } else { return 0; } } int main(void) { char input; printf("> "); scanf(" %c",&input); int output = is_hex_digit(input); printf("%d",output); return 0; }