Radio Shack TRS-80 Model II Reference Manual page 172

Modell! TRSDOS
PRTBKSP
Modify Printer Driver for Backspacing
Some printers are capable of backspacing for the purpose of overprinting and other
special applications, For example, the Radio Shack Daisy Wheel printers have this
capability,
The TRSDOS printer driver ordinarily ignores the backspace code (ASCII
X'os').
If
you are using a printer which can handle this code properly, you may want to
modify TRSDOS so that it will send the backspace code to the printer.
To make the modification, execute the Do-file named PRTBKSP. This will make a
permanent change in the TRSDOS diskette. The change will not take effect until the
Computer is started or reset using the modified TRSDOS,
After the modification has been made, TRSDOS will send the backspace character to
the printer, and will decrement the character-in-line count.
Sample Use
DO PRTBKSP
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