A[row][col]

*(A+1)

*((A+1)+1)

int get_highest(int *a, int cols, int row, int col)
{
   int i, j;
   int highest = *a;
   for( i = 0; i < row; i++)
      for( j = 0; j < col; j++)
         if ( *(a + i*cols + j) > highest)
            highest = *(a + i*cols + j);
   return highest;
}