CTRL-PRTSC:  Turns on "printer echo."  When printer echo is on, information
displayed on the screen is also sent (echoed) to the printer.  Turn on printer
echo by holding down the CTRL key and then pressing the PRTSC key.  Turn printer
echo off by pressing CTRL-PRTSC again.

On the Tandy 1000:  Press the PRINT key to turn printer echo on and off.

On the PCjr:  Hold down FN and press ECHO to turn printer echo on and off.
