//I received an error: Crash (ACCESS_VIOLATION) from the judge

// USU Problem 1146
// Maximum Sum
// Done by Teh Ming Han

#include <iostream.h>
#include <fstream.h>

int main(){
   int x1,y1,x2,y2,n,c,max=0;
   int sum[100][100], work[100][100]={0};

   ifstream infile("maxsum.in");
   infile>>n;
   for (x1=1;x1<=n;x1++)
      for (y1=1;y1<=n;y1++)
         infile>>sum[x1][y1]; //read data
   infile.close();

   for (x1=1;x1<=n;x1++)
      for (y1=1;y1<=n;y1++)
         for (x2=1;x2<=x1;x2++)
            for (y2=1;y2<=y1;y2++)
               work[x1][y1] += sum[x2][y2];

   for (x1=1;x1<=n;x1++)
      for (y1=1;y1<=n;y1++)
         for (x2=x1;x2<=n;x2++)
            for (y2=y1;y2<=n;y2++){
               c = work[x2][y2] - work[x1-1][y2] - work[x2][y1-1] +
work[x1-1][y1-1];
               if (c>max) max=c;
            }

   ofstream outfile("maxsum.out");
   outfile<<max;
   outfile.close();
   return 0;
}

N may be as large as 100

lucky~

As I see your program is O(N^4) and it's to many operations when N = 100.

your algo is good, theoretically is N^4 but practically fits in time.
First you must not use files, and second put 200 or 110 or something little larger than 100. You'll get AC (I sent your source with these modifications).

u use files.
try using scanf/cin
printf/cout

use
for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++) {
        b[i][j] = b[i - 1][j] + b[i][j - 1] - b[i - 1][j - 1] + a[i][j];
    }
}