SR-56 f(n) Curiosity

[Dave Britten]

I think in most cases, we can answer questions starting with "Why did TI..." with "it was easier/cheaper to build that way". Which isn't to say that TI calculators are wildly inferior, just that they often used extra RAM to allow for simpler instruction decoding or ROM routines. For example, the TI-59 is a byte-oriented, BCD machine, and while each program step is stored as a full byte, only instructions with decimal digits are used. That's 100 out of 256 possible instructions that were actually used! There was plenty of room in the instruction table to merge INV with other instructions (beyond the couple where they did, like INV SBR/RTN), but they opted for a simpler-yet-RAM-wasteful design.