Radio Shack TRS-80 Model II Reference Manual page 103

Library Commands
First turn the spooler on, and begin capturing printer output in
SPOOL I:
SPOOL ON
SPOOL N, F
=
SPOOL1
Now use the Computer normally, until you are ready to begin printing out
SPOOL 1.
When you are ready, type:
SPOOL N, F
=
SPOOL2
This closes
SPOOL!,
and makes
SPOOL2
the new capture-file. To begin printing
SPOOL!,
type:
SPOOL P, F
=
SPOOL1
Now
SPOOL!
will be printed, and any real-time printing will be saved in
SPOOL2.
Suppose you want to halt the print-file operation. Then type:
SPOOL H
This does not affect the capture-file operation. To resume printing, type:
SPOOL R
Using the Spooler
1. Spooler is invoked by the console command:
SPOOL ON.
This will cause a
high-memory module to be loaded and linked with the operating system.
Whenever spooler is active (resident in high-RAM), the user must insure that this
high-RAM space is not overlayed with any programs or subroutines.
2. Before getting into the details of spooler, a brief explanation of how it works is
in order. Spooler itself can be thought of as a high level' 'supervisor" whose
role is to monitor the use of the "physical" printer. As such, spooler can be said
to "control" or "own" the printer. Spooler will accept your commands to print
out disk files of text to the real printer and will, upon your command, save all
data which was intended to be printed onto a disk file.
As long as spooler is active (or until you.issue the command line:
SPOOL OFF),
all data that would normally go to the printer will be intercepted by spooler. This
is called the' 'capture" function of the spooler. "Capturing" can be done to a
disk file of the name you specify in the command line:
SPOOL N F
=
filespec
"Capturing" can also be done such that all of the printed data bytes will get
"thrown" away - this is called capturing to a dummy file.
In this case, no file
is opened and no data gets saved. There is a good use for this, as we will discuss
later. Because of this capturing function, your program is now said to be
outputting data to a "logical" printer, notthe "physical" printer.
139