HP-style Keycode for TI-58/59

[Thomas Okken]

Fully merged keystrokes, as implemented in the Woodstocks, means you can only have 256 different instructions, because each program line is one byte of RAM. In the HP-29C and HP-67, they had to sacrifice instructions to make everything fit in the available opcode space, which is why they both have registers that aren't directly addressable, and the 67 has no STO arithmetic on registers A-E and I.

The TI-58 and -59 have so many registers, directly accessible and with arithmetic on the whole range of 00-99, plus tons of labels *and* line number addressing, that it was always going to need multi-byte instructions. The same is true for the HP-41C, incidentally, but the 41C hides it better, by making all instructions, no matter how many bytes long they are, appear in the display as just one line. I assume TI had something like that on the drawing board, too, but HP beat them to it.