Why does -2^2 compute to -4 on my HP Prime?

[Steve Simpkin]

The order of precedence used by algebraic scientific calculators has changed over the years. Early Texas instruments (TI) models like the SR-50 (Sum of Products logic) and TI-52/TI-30/TI-57/TI-58/TI-59, etc (AOS logic) would square the number in the display immediately after pressing the X^2 key (like RPN calculators). This would treat the sign of the number as an integral part of the number so -2^2 would equal 4. This is identical to the way HP RPN models calculated this type of problem.

For Texas Instruments, the change in logic occured around 1990 with the TI-81 (EOS logic). Theses and later models would treat the - as a negation operator with a lower precedence than the ^2 function so -2^2 would equal -4 on these models. This is described in more detail on the Datamath site:
http://www.datamath.org/Sci/WEDGE/SR-52_...ing_System: