Column-major pattern

A bi-dimensional array memory access follows a column-major pattern when iterating over the columns sequentially, then doing the same for each row within the column.

for (int j = 0; j < N; j++) {
  for (int i = 0; i < N; i++) {
    A[i][j] = ...
  }
}

Note in the pseudocode that the outer loop drives the second dimension of the array while the inner loop drives the first dimension.