IBM Personal Computer XT Manual To Operations page 201

The functions of the Escape key, also are described in
your operating system or application program manual.
(G}I]
The Tab key moves the cursor to the next tab stop.
Tab stops are defined in your operating system or
application program manual.
The keyboard has two shift keys, which are in the
typewriter area. Pressing either of these changes the
keys in the typewriter area to the uppercase mode.
When alphabetic keys are pressed, the characters
appear as capital letters. When other keys in the
typewriter area are pressed, the characters shown on
the upper portion of the keys appear.
Keyboard 3-9