TRS-80 MODEL III
Printer
ControlFeatures
Output to a printer involves several variables:
..
Maximum line width (How many print columns are there?)
• Page length (How many print lines are on a page?)
..
Printerstatus (Is the printerconnected and ready to receive data and print it?)
In this section, we will explain how to set up the Model III to control all these
variables.
Settingthe Maximum Line Length
In Model III BASIC, you can preset the maximum line length.
If
a line exceeds the
preset length, the Computerwill automatically insert an end
of
line (carriage return)
so that the rest
of
the line will be output on a new line. The following paragraphs
explain why you may want to do this.
One important difference between display output and printer output is the
maximum line length. (A "line" is a stream
of
data characters terminated by a
carriage return
(ENTER).)
The Model III Display has a maximumline length
of
64 characters.
If
you PRINT a
line longer than this, the Computer
simply'
'wraps around" to the beginning
of
the
next line.
Printers have a maxirnum line length, too, but this length differs for various
models. Theresponse to an overflow (longer than maximum-length) line also
varies. Some models wrap around to the next line automatically. Others may lose
the extra data, and maybegin abnormal operation when the line is too long.
Anotherconsideration is paperwidth. Suppose yourpaper
is
only wide enough to
hold 80
characters-but
the printerwill accept lines
of
up to 132 characters. In this
case,
if
you send a line longerthan 80characters, the printerwill printpart
of
the
informationpast the edge
of
the paper.
How toSetthe Line
Length
Memory address 16427 contains a value equal to the maximum line length
less.
two.
Forexample, to set the maximum line length to
64, execute the BASIC statement:
POKE 16427, 62
Since the Display is 64 characters per line (cpl), this setting will make line printer
output match Video Display output.
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