Epson Apex 20020 - Manual (Page 56)

The Num Lock,
Scroll
Lock, and Caps Lock keys work as
toggles; press the key once to turn on a function and again to
turn it off. When the function is enabled, the corresponding
light on the top right comer of the keyboard is on. When the
function is disabled, the light is off.
Stopping a Command or Program
You may sometimes need to stop a command or program while
it is running. Many application programs provide a command
you can use to stop or even cancel (undo) an operation. If you
have entered an MS-DOS command that you want to stop, try
one of the following commands:
Hold down the Ctrl key and press C
Hold down the Ctrl key and press Break.
These methods may also work in your application programs. If
you cannot stop a particular operation, however, you may need
to reset the computer, as described in the following section.
Caution
It is best not to turn off the computer to stop a program or
command. If you have created new data that you have not
yet stored, it will be erased if you turn off the computer. Your
computer stores data in its memory until you save it; but the
memory area is erased each time you turn off or reset the
computer.