Graphics

The graphics commands

The graphics mode commands are quite different from other commands used by the printer. For most of the other printer modes, such as emphasized and double-wide, one ESC code turns the mode on and another turns it off. The graphics commands are more complicated because the code that turns on the graphics mode also specifies how many columns of graphics will be printed. After the printer receives this command, it interprets all subsequent numbers sent to the printer as column patterns, until the specified number of columns has been printed.

While there are alternate commands for four of the most commonly used options (see Chapter 9), your printer has one special command that allows you to use any of the seven graphics options. The format of the command is:

ESC * m n1 n2 data

In this command, m selects the graphics option and n1 and n2 specify the number of columns to reserve for graphics. The available graphics options are listed below.

Option

m

Horiz. density (dots/in.)

 

 

 

 

 

Single-density

 

60

 

Double-density

 

120

 

High-speed double-density*

 

120

 

Quadruple-density*

 

240

 

CRT I

 

80

 

Plotter (1:l)

 

72

 

CRT II

 

90

 

 

 

 

 

*Adjacent dots cannot be printed in this mode.

4-12Software and Graphics