IBM PCjr Manual page 51

Amazing what you can do with these function keys!
If you would hke to continue the music, just press the
Fn key and F2 key again.
If you want to stop the music at any time, press the Fn
key and then the Break key. This key combination is
used when you want to stop a program that is running.
Let's do that now.
Press the Fn key; release it. Now
press the Break key.
then
You just saw that the Fn key can also be used with
special letter keys as well as number keys to perform
functions.
By the way, remember when we told you that the
computer had a good memory? We're going to prove
that to you now.
Press the Fn key and then the FIO
key. Now watch the top of your
screen.
Getting Started 2-35