My observations and guesses, as well as (hopefully) time saving information.
The 3-letter characters are the ascii names for certain commands.
Here is a list of all the ones I can find and their control shortcuts.
All Ascii Special characters Black
DC1- XON, with XOFF to pause listings; ":okay to send" - ^Q
RS - Record separator, block-mode terminator - ^^
ETX - End of text - ^C
ESC - Escape, next character is not echoed - ^[
ETB - End transmission block, not the same as EOT - ^W
US - Unit separator - ^_
BEL - Bell, rings the bell… - ^G
% - Modulo
ENQ - Enquiry, goes with ACK; old HP flow control - ^E
NUL - Null Character - ^@
NAK - Negative acknowledge - ^U
VT - Vertical tab - ^K
EOT - End of transmission, not the same as ETB - ^D
ACK - Acknowledge, clears ENQ logon hand - ^F
DC3 - XOFF, with XON is TERM=18 flow control - ^S
SYN - Synchronous idle - ^V
CR - Carriage Return - ^M
EM - End of medium, Control-Y interrupt - ^Y
DC2 - Device control 2, block-mode flow control - ^R
FF - Form Feed, page eject - ^L
SOH -Start of heading, = console interrupt - ^A
DC4 - Device control 4 -^T
DLE - Data link escape - ^P
BS - Backspace, works on HP terminals/computers - ^H
CAN - Cancel line, MPE echoes !!! - ^X
FS - File separator - ^\
STX - Start of text, maintenance mode on HP console - ^B
SO - Shift Out, alternate character set - ^N
White Exclusive Characters
LF - Line Feed - ^J
SUB - Substitute - ^Z
SI - Shift In, resume default character set - ^O
Assuming that SO and SI do mean to change character set, what is this alternate set? Does the use of SO in black, and SI in white indicate that we should follow ones instructions, blacks, first, then white's?
Do we use the letters in the control keys as a guide for substitution?
Also, note that there are codes for 4 different input devices. Do they each have their own code or set of instructions?
Python Image Code:
m+=n means to take m, and increment it by n
x**2, means x squared
a**3, means a cubed
t**-1, means 1/t
l[i], means the i-1th item or letter in l, as positions start from zero in python.
Might they be instructions?
Assuming that x is a set of 0 to 7 means for x from 0 to 7, the graph looks like this: with peaks of 7 high.