how do i chunk a 1000MB file using mmapdemo - c

Question

I'm following a tutorial from BeeJ's website and i've learnt quite a bit of it.
I'm in that stage of experimentation and want to somehow build upon this code.
In short, say the user types an address: 1050576 for a file that's roughly 1000MB, the program (shown below) should map the chunk in the file data up to a position where 1050576 falls between chunk beginning and its length.
When i run the code, it says the max address size is 924 and so i can't really chunk a file that's 1000mb.
Could someone help explain / provide an example on how i can tackle this?
/*
** mmapdemo.c -- demonstrates memory mapped files lamely.
*/
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <errno.h>
int main(int argc, char *argv[])
{
int fd, offset;
char *data;
struct stat sbuf;
if (argc != 2) {
fprintf(stderr, "usage: mmapdemo offset\n");
exit(1);
}
if ((fd = open("mmapdemo.c", O_RDONLY)) == -1) {
perror("open");
exit(1);
}
if (stat("mmapdemo.c", &sbuf) == -1) {
perror("stat");
exit(1);
}
offset = atoi(argv[1]);
if (offset < 0 || offset > sbuf.st_size-1) {
fprintf(stderr, "mmapdemo: offset must be in the range 0-%ld\n", sbuf.st_size-1);
exit(1);
}
if ((data = mmap((caddr_t)0, sbuf.st_size, PROT_READ, MAP_SHARED, fd, 0)) == (caddr_t)(-1)) {
perror("mmap");
exit(1);
}
printf("byte at offset %d is '%c'\n", offset, data[offset]);
return 0;
}