Keystroke programming

These TI calculators allowed for addressing up to 100 data memory locations, numbered 00 to 99 (some models had a lower limit than this).

A keystroke sequence like STO  4   2  (store the currently-displayed number into memory 42) would be encoded as 42 42.

A code sequence like 61 11, on the other hand, represents the keystrokes GTO  A , which is a branch to the location marked by the symbolic label  A .

INV invoked the "inverse" (whatever that meant) of the following function, and was recorded in a program as a separate keystroke (code 22), while 2nd invoked a completely different function which was written on the keypad faceplate just above the key.

Here is the table of the codes produced with the 2nd prefix: The Ind key allows for indirection: wherever a reference to a memory register or a program location is allowed, this key can be used to fetch the actual value from a memory register.

Note the use of code 92 for INV SBR (return from subroutine); this was not necessary for reasons of ambiguity, but was done to save space with such a common sequence.