IBM PCjr Manual page 36

You have just seen how using the cursor control keys
moves the cursor to letters you want to change. The
process of changing what you type is called editing.
You have also seen that you can use a Shift key to make
uppercase letters and the CapsLock key to lock your
keyboard in uppercase.
A few words now about the most important key on the
keyboard - the Enter key. This key is on the right side
of your keyboard just above the right Shift key.
oddoddddddSl.-lld ti
OOOOOOPODOijbtJ HI
D OODDOODDDOcklJo
CP OODOODDDODCP DO
D ' ' ODD D
Remember the strange object in the upper left corner of
the last screen? Do you remember how it disappeared
from the screen when P.C. moved through it? That
object was the Enter key. It was the key that allowed
P.C. to "enter" into the next adventure by opening the
box.
Just as it helped P.C. enter the box, the Enter key will
do special things for you. It will carry your messages to
the computer and allow you to give the computer a
command or deposit information into its memory.
2-20 Getting Started