Matrix Multiplication in C++

matrices.cpp

#include <iostream>

int main(int argc, const char * argv[]) {
    int n = 800;
    int a[n][n], b[n][n], mult[n][n], i, j, k;

    for(i = 0; i < n; ++i)
        for(j = 0; j < n; ++j)
            a[i][j] = 1;

    for(i = 0; i < n; ++i)
        for(j = 0; j < n; ++j)
            b[i][j] = 1;

    for(i = 0; i < n; ++i)
        for(j = 0; j < n; ++j)
            mult[i][j]=0;

    std::cout << std::endl << "Starting after matrix initialization..." << std::endl;
    clock_t tStart = clock();

    for(i = 0; i < n; ++i)
        for(j = 0; j < n; ++j)
            for(k = 0; k < n; ++k)
                mult[i][j] += a[i][k] * b[k][j];

    std::cout << std::endl << "I did it in "<< (double)(clock() - tStart)/CLOCKS_PER_SEC << "sec" << std::endl;
    
    for(i = 0; i < 5; ++i)
    for(j = 0; j < 5; ++j)
    {
        std::cout << " " << mult[i][j];
        if(j == 4)
            std::cout << std::endl;
    }

    return 0;
}