IBM 5150 Manual To Operations page 86

Some Keys You Will Use with DOS
In addition to the keys you'd find on a typewriter, your
keyboard has some special keys you'll use with DOS.
Before we get to the special keys, here are a few
~
differences between your keyboard and a typewriter, ~
j
that you need to know.
Characters That Look Alike­
Oh's and Zeros, Ones and Els
Computers are fussy about the number
zero and the letter O-they want
what they want, and you can't fool
them into taking the wrong one.
Make sure you type the right key in
commands and filenames.
On our printer, the letter 0 looks a
little squarer than the number O.
On our screen, the number zero has a
diagonal line through it, something
like this:
(/J
If you are used to typing a lowercase
L for the number 1 (if you have used
a portable typewriter a lot, for
example), you'll have to break that
habit.
Again, the computer knows the
difference. Use the number key
when the number I is required, as in a
filename such as DATAI23. (Now if
you were to use lowercase L when
creating a filename, that's okay. Just
be sure to use it again when you want
to use that file!)
DOS 3-12