# Arrays tutorial 1a

Program | Comments
    //Arrays - Tutorial 1
    #include <iostream>
    #include <iomanip>
| We need iostream.h since we are using cout and we need iomanip.h (io manipulators header file) since we use the setw() manipulator.

    { int
       num[10][10],
       totals[]
        = {0,0,0,0,0,0,0,0,0,0};
      int row, column;
| The num array is declared as being a two-dimensional 10 X 10 array of integers. The totals array does not have a size declared but initialised to zeroes, the number of zeroes determines the size of totals. The integers row and column are used to count through the 2D array.

      for (row = 0; row < 10; row++)
        for (column = 0; column < 10; column++)
          num[row][column] = row * column;
| Array num is initialised to contain the product of the current values of row and column. A nested for loop is used, the program steps through in row order followed by column order.

      for (column = 0; column < 10; column++)
       for (row = 0; row < 10; row++)
        totals[column]
         = totals[column] + num[row][column];
| Now the totalling of each column is completed. A nested for loop is used: for each row total the current column.

      for (row = 0; row < 10; row++)
       { cout << "....... ";
         for (column = 0; column < 10; column++)
          cout << setw(4) << num[row][column];
         cout << endl;
       }
| The rows and columns are displayed almost as for the original example. The difference is just the addition of the line: cout << "....... ";

      cout << "Totals: ";

      for (row = 0; row < 10; row++)
       cout << setw(4)
            << totals[row];

      cout << endl;

      return 0;
    }
| Last of all the totals are shown, after the last row of the num array.

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