mem.c

#include <stdio.h>
#include <stdlib.h>

#define COUNT 100000
#define BLOCKSIZE 1000

int main(int argc, char *argv[])
{
    char **ptr;

    printf("No heap memory has been allocated yet.\n");
    printf("Press enter to continue.\n");
    getchar();

    ptr = malloc(COUNT*sizeof(char *));
    if(!ptr){
        printf("Out of memory.\n");
        return 1;
    }

    /* Allocate a load of memory. */
    for(int i=0; i<COUNT; i++){
        ptr[i] = calloc(BLOCKSIZE, 1);
        if(!ptr[i]){
            printf("Out of memory.\n");
            return 1;
        }
    }

    printf("There has now been %ld bytes of heap memory allocated.\n", COUNT*sizeof(char *) + COUNT*BLOCKSIZE);
    printf("Press enter to continue.\n");
    getchar();

    /* Free up all of those blocks apart from the last one. */
    for(int i=0; i<COUNT-1; i++){
        free(ptr[i]);
    }


    printf("All but %ld bytes of the heap memory has now been freed.\n", COUNT*sizeof(char *) + BLOCKSIZE);
    printf("Press enter to continue.\n");
    getchar();

    free(ptr[COUNT-1]);
    free(ptr);

    printf("There should now be no heap memory allocated.\n");
    printf("Press enter to continue.\n");
    getchar();

    return 0;
}