Which ordering of nested loops for iterating over a 2D array is more efficient [duplicate]

Question

Which of the following orderings of nested loops to iterate over a 2D array is more efficient in terms of time (cache performance)? Why?

int a[100][100];  for(i=0; i<100; i++) {    for(j=0; j<100; j++)    {        a[i][j] = 10;        } } 

or

for(i=0; i<100; i++) {    for(j=0; j<100; j++)    {       a[j][i] = 10;        } } 

Answer 1

The first method is slightly better, as the cells being assigned to lays next to each other.

First method:

[ ][ ][ ][ ][ ] .... ^1st assignment    ^2nd assignment [ ][ ][ ][ ][ ] .... ^101st assignment 

Second method:

[ ][ ][ ][ ][ ] .... ^1st assignment    ^101st assignment [ ][ ][ ][ ][ ] .... ^2nd assignment