#include <stdio.h>
#include <string.h>

int main() {

	void to_upper_case_string(char *);

	char string[100];

	printf("Enter string: ");
	gets(string);

	to_upper_case_string(string);

	printf("In upper case: %s", string);

	return 0;
}

void to_upper_case_string(char *string) {
	void to_upper_case(char *);
	int length = strlen(string);
	for(int i = 0; i < length; i++) {
		to_upper_case(&string[i]);
	}
}

void to_upper_case(char *c) {
	int within_bounds(int, int, int);
	if(within_bounds(*c, 'a', 'z')) {
		*c -= 32;
	}
}

int within_bounds(int x, int low, int high) {
	if(x >= low && x <= high) return 1;
	return 0;
}