16C internal floating point format?

[billf]

Hi Thomas and/or all,

One other behavior question: What happens when you try to enter the following program?

G SF 9

How about

G SF A

My theory is that they behave differently: I think the calculator will let you enter SF-9 as a program instruction, BUT executing that program instruction is guaranteed to generate an "Error 1". On the other hand, I'm betting it won't let you enter SF-A at all. Is my guess accurate?

What I see is that the back of the calculator (according to an image I have) says that "Error 1" can mean "F > 5," so it must let you input invalid flag numbers. However if I set the max at F (15), I get too many opcodes -- when I limit it to 9, I get 255 opcodes, which makes total sense. This even means 0 is left over as NOP, which maybe they use internally when running off the end of a program, since it looks like the number of program lines is stored internally divided by 7.

It's a little weird that they allow entry of invalid flag numbers in program opcodes, but maybe that aligns the instruction set of the 16C with the 15C or something.

This really was a superbly engineered calculator.