Most of the computer terminals at the Stanford AI Lab are display
terminals; a few are vector-oriented, built by Information
International, Inc. (hereafter called IIIs) and the rest use
standard TV monitors built by Ball Miratel (hereafter called
Data Discs because the controller for them was built by Data Disc).
These terminals use keyboards which generate an extended version
of the usual ASCII character set.  The normal 7-bit ASCII codes are
all used for graphic characters, and control functions are provided
by two extra bits generated by the CONTROL and META keys.  Thus,
while the CONTROL key on a standard ASCII terminal subtracts 100 (octal)
from the character code, our CONTROL key adds 200 and our META key
adds 400.  Also, two special keys, ESC (escape) and BREAK, generate
special codes which are not transmitted to user programs at all, but
are directly interpreted by the timesharing monitor as special
commands affecting the terminal.  These commands are explained at
length in Section 2 of the Monitor Command Manual, SAILON 54.3,
which is available online in the file MONCOM.BH[S,DOC].  If you
are logged in at a display terminal, you can print a concise list
of ESC and BREAK functions, and a table of the extended ASCII character
codes, on the Xerox Graphics Printer by typing HELP DDKEY if you are
using a Data Disc or HELP IIIKEY if you are using a III.  The list
is designed to fit in the indentation provided for the purpose at the
top of the keyboard.