mem.c

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

#define PADDING 255

void fill(unsigned char* addr, size_t buffer) {
    unsigned long i;

    for (i = 0; i < buffer; i++) {
        *(addr + i) = PADDING;
    }
}

int main(int argc, char **argv) {
    unsigned char *segment;
    size_t buffer = 1 << 30;

    segment = malloc(4*buffer);

    printf("Filled %zu bytes starting at %zx with %x\n", buffer, segment, PADDING);
    fill(segment, buffer);
    getchar();

    return 0;
}