Unit installation

With this numbering system any combination of the seven pins

adds up to a number between 128 and 255, and no numbers are dupli-

cated.

Now that you know the principles of dot graphics, here are two

simple exercises and a more complex example that shows you how to

design your own graphics.

One-Line Graphics Program

Your first graphics exercise is a program that prints a single pattern

of dots 40 times. Type it in first, and then read the explanation that

follows.

NEW

10 OPEN4,4

20 PRINT#4,CHR$(8);

FOR X=1 TO

PRINT#4,CHR$(213);

50 NEXT X:PRINT#4

60 CLOSE4

Line 10 opens a file, as usual. Then line

sends the graphics com-

mand to the printer. Notice that this line ends in a semicolon. The

semicolon keeps the graphics command on the same print line as the

pin numbers that you will send in line 40. The graphics command

stays on for only one print line. Therefore, you must be careful not to

put it on a separate print line from the pin numbers, and you must

send it several times if you are printing several lines of graphics.

Lines 30 and 50 set up a loop so that the pin number is sent 40 times.

Line 40 contains the pin number (213) that is sent to the printer 40

times. In Figure

4-2

you can see the pattern that this number produces.

Again be sure that you have typed in the semicolon in this line so that

all

repetitions of the pin number will be on the same print line. Line

closes the file, as usual.

Now that you know how the program works, run it to see the result

below. Although it does not look as interesting as the examples at the

beginning of this chapter, the program does allow you to see exactly

how the graphics mode works.