Chapter 1 Introduction to PRESCRIBE
1-2
Entry and Exit
The printing system can be thought of as having a multiple personality. When its power
is switched on, it performs the normal printing system functions of printing out files and
other data. Application software can control the printing system using one of the seven
emulations. When the printing system uses an emulation, it is said to be printing in emu-
lation mode.
PRESCRIBE is an additional mode of operation in which the printing system under-
stands data it receives not as text to be printed, but as commands to be executed. The
PRESCRIBE mode is available at any time during operation from any emulation mode.
The initializing string that takes the printing system from the usual text-printing mode
into the PRESCRIBE mode is !R!. The command that returns it from the PRESCRIBE
mode to the emulation mode is EXIT;. These transitions are diagramed in the figure
below.
Figure 1. 1. Mode Transitions
The printing system’s emulation mode can be permanently set by the FRPO (Firmware
RePrOgram) P1 command. See Chapter 7 for details. The printing system is factory-set
to emulate the Hewlett-Packard LaserJet.
The example below shows how these transitions can be used in a file. The lines begin-
ning with !R! are PRESCRIBE commands. Note how each block of commands begins
with !R! and ends with EXIT;. These sections are not printed; instead, they set margins,
select three different fonts, and draw a box around one line of text. The remainder of the
file consists of ordinary text, and is printed out as shown in the figure on the next page.
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