What's the difference in memory or similar between the next two codes when i create a new array, cause in the first case (array inside main) the message of jugde is "Run time error/Stack overflow" and in the second case (array outside main) the jugde accept the code:

Case 1:

#include <stdio.h>
#include <math.h>
int main(){
    double array[128*1024];
    int i = 0;
    unsigned long long n;
    while (scanf("%llu", &n) != EOF) {
        array[i++] = sqrt(n);
    }
//Code for print......



Case 2:

#include <stdio.h>
#include <math.h>
double array[128*1024];
int main(){
    int i = 0;
    unsigned long long n;
    while (scanf("%llu", &n) != EOF) {
        array[i++] = sqrt(n);
    }
//Code for print......

In example 1 array is allocated on stack, in example 2 - on global memory
http://stackoverflow.com/questions/408670/stack-static-and-heap-in-c

My opinion:
- stack is small;
- stack size is unpredictable.
Conclusion: there shouldn't be big variables on stack. There shouldn't be recursion with more than logarithm complexity. If recursion depth is above 100 then it isn't usable for practical purpose.

Note: STL containers aren't big despite dozens of elements inside.
They use heap to hold elements and don't spend too much stack size.
So here is ok:
int main() {
    std::vector<double> array(128*1024);
...

Thank you very much for the clarification..and link of course.