Using the free() function

/* 1702.c: Using the free() function */
#include <stdio.h>
#include <stdlib.h>
/* function declarations */
void DataMultiply(int max, int *ptr);
void TablePrint(int max, int *ptr);
/* main() function */
main()
{
    int *ptr_int, max;
    int termination;
    char key = 'c';

    max = 0;
    termination = 0;
    while (key != 'x'){
        printf("Enter a single digit number:\n");
        scanf("%d", &max);

        ptr_int = malloc(max * max * sizeof(int)); /* call malloc() */
        if (ptr_int != NULL){
            DataMultiply(max, ptr_int);
            TablePrint(max, ptr_int);
            free(ptr_int);
        }
        else{
            printf("malloc() function failed.\n");
            termination = 1;
            key = 'x'; /* stop while loop */
        }
        printf("\n\nPress x key to quit; other key to continue.\n");
        scanf("%s", &key);
    }
    printf("\nBye!\n");
    return termination;
}
/* function definition */
void DataMultiply(int max, int *ptr)
{
int i, j;

for (i=0; i<max; i++)
for (j=0; j<max; j++)
*(ptr + i * max + j) = (i+1) * (j+1);
}
/* function definition */
void TablePrint(int max, int *ptr)
{
    int i, j;

    printf("The multiplication table of %d is:\n",max);
    printf(" ");
    for (i=0; i<max; i++)
    printf("%4d", i+1);
    printf("\n ");
    for (i=0; i<max; i++)
    printf("----", i+1);
    for (i=0; i<max; i++){
        printf("\n%d|", i+1);
        for (j=0; j<max; j++)
        printf("%3d ", *(ptr + i * max + j));
    }
}