Here's a grid you can use to layout the calculator applet. Notice
that there are more cells than there are components in the
calculator. Some of the components in the calculator occupy more
than one cell of the grid. For example, the TextField occupies the
four cells (0, 0), (1, 0), (2, 0), and (3, 0).
| (0, 0) | (1, 0) | (2, 0) | (3, 0) |
| (0, 1) | (1, 1) | (2, 1) | (3. 1) |
| (0, 2) | (1, 2) | (2, 2) | (3, 2) |
| (0, 3) | (1, 3) | (2, 3) | (3, 3) |
| (0, 4) | (1, 4) | (2, 4) | (3, 4) |
| (0, 5) | (1, 5) | (2, 5) | (3, 5) |