The width of one space invader in this program is 12-dot positions (plus one blank space). This means that 13-dot positions are enough data to describe a single invader. We will use a series of 20 invaders for this program. This gives you a total of 260 (13 x 20) dot positions for data.

To find n1 and n2, divide 260 by 256 and you get a quotient of 1 with a remainder of 4. Enter 4 as the value for n,, and 1 as the value for n2. Enter these values with a comma between them.

The program then asks you how many data per space invader. Enter 13 and press RETURN.

The program now asks the order of the data for a single invader. The data numbers are shown at the bottom of Figure 6-3. Enter them one at a time, pressing RETURN after each data number. The program prompts you by showing DATA? each time. Once you enter the last data number, the program prints out.

Figure 6-3. Data for space invader

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