C: Deallocate Memory

#include <stdio.h>
#include <stdlib.h>
/* declare global var's */

int hamming_length=0, parity_type=-1;

/* declare & initialize hamming string */

char *hamming = NULL;

/* Option #1 */

void params() {
	printf("Enter the length of the Hamming code: ");
	scanf("%d", &hamming_length);
	printf("Enter the parity (o=even, 1=odd): ");
	scanf("%d", &parity_type);

	hamming = (char *) malloc (hamming_length * sizeof(char));
}

/* Option #2 */

void check_hamming_code() {
	/* declare local var's */
	
	int i,j,k, error_bit=0;

	/* prompt for hamming code string */
	printf("Enter the Hamming code: ");
	scanf("%s",hamming);

	for(i=1; i < hamming_length; i*=2) {
		int current_parity = parity_type;

		for(j=i; j <= hamming_length; j+=2*i) {

			for(k=j; (k <= hamming_length) && (k < i+j); k++) {
				
				if(k != i) 
					current_parity = current_parity ^ (hamming[hamming_length-k]-'0');
			} /* end of k loop */
		} /* end of j loop */
		error_bit = error_bit + (current_parity ^ (hamming[hamming_length-i]-'0'))*i;
	} /* end i loop */

	/* correct error bit */

	if(error_bit == 0)
		printf("There is no bit error\n");
	else {
	printf("There is an error in bit: %d\n",error_bit);

	if((hamming[hamming_length - error_bit]-'0') == 0) {
		hamming[hamming_length - error_bit] =  (hamming[hamming_length-error_bit] +1);
	}
	else {
		hamming[hamming_length - error_bit] =  (hamming[hamming_length-error_bit] -1);
	}
	printf("The corrected Hamming code is: %s\n", hamming);
	}
}

/* Option #3 */

void exit_program() {

	if(hamming != NULL)
		free(hamming);
}

int main() {
	/* declare local var's */

	int menu_option = 0;

	while(menu_option != 3) {
		printf("\n");
		printf("Error detection/correction:\n");
		printf("------------------------------------\n");
		printf("1) Enter parameters\n");
		printf("2) Check Hamming code\n");
		printf("3) Exit\n");
		printf("\n");
		printf("Enter selection: ");
		scanf("%d",&menu_option);
		printf("\n");

		switch (menu_option) {
		case 1: params(); break;
		case 2: check_hamming_code(); break;
		case 3: exit_program(); break;
		default: break;
		} /* exit switch statement*/
	} /* exit while statement*/
	return 0;
}

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