Evolution of Conditional Tests

[David Hayden]

I noticed recently that the conditional tests available on the programmable models changed over the years. Here they are in roughly chronological order from the 65 to the 15C:

Code:

    x<y x<0  x<=y x<=0  x>y x>0  x>=y x>=0  x!=y x!=0  x=y x=0
65             Y         Y                    Y         Y
55             Y                                        Y
67       Y     Y         Y   Y                Y    Y    Y   Y   ( x=y and x=0 added thanks to Dave Britten's reply below.)
25   Y   Y                         Y    Y     Y    Y    Y   Y
29C      Y     Y         Y   Y                Y    Y    Y   Y
33C      Y     Y         Y   Y                Y    Y    Y   Y
34C      Y     Y         Y   Y                Y    Y    Y   Y
38C            Y                                            Y
41C  Y   Y     Y    Y    Y   Y                Y    Y    Y   Y
10C            Y                                            Y
11C      Y     Y         Y   Y                Y    Y    Y   Y
15C  Y   Y     Y    Y    Y   Y     Y    Y     Y    Y    Y   Y

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.