Graphics

With this numbering system, any combination of the eight nozzles adds up to a decimal number between 0 and 255, and no numbers are duplicated.

Since there are 24 nozzles in each column, you must make a calculation for each of the three sections in each column. As you can see, this method of planning and printing dot graphics requires considerable calculation. Because triple-density uses 180 columns per inch, printing a single line of triple-density graphics only one inch long requires 540 numbers. Fortunately, commercial software can do the calculations for you.

Before you can put these numbers in a graphics program, however, you need to know the format of the graphics command.

The graphics command

The graphics mode command is quite different from the other commands used by the printer. For most of the other printer modes, such as emphasized and double-width, one ESCape code turns the mode on and another turns it off. For graphics, the command is more complicated because the code that turns on a graphics mode also specifies how many columns it will use. After the printer receives this code, it interprets the next numbers as nozzle patterns and prints them on the paper.

Your printer has one command that allows you to use any of the 11 graphics options. The format of the command is:

ESC * m n1 n 2 data

Software and Graphics 4-13