Evolution of Conditional Tests

[rprosperi]

(01-03-2020 09:28 PM)David Hayden Wrote:  It's particularly interesting to me to see how things changed from the 67 to the 25 to the 29C. And look at how the 25 was the only calculator with an x<y test until the 41C. The others all used x<= y. Instead of x>y and x>0, the 25 had x>=y and x>0, functions that wouldn't appear again until the 15C. I wonder why HP kept changing their mind.

Intro Dates:

HP-25: 1975-8-1
HP-67: 1976-7-1
HP-29C: 1977-7-1

So at least for these three models (and noting Dave's correction) they really only changed their mind once.

I too used to instinctively react thinking the 67 came out before the 25; it was a similar discussion here a couple years ago that made me research the dates to better understand. It also answers why the 29C seems so different from the 25, but not really not so different from the 67.