DM42 and labels

[Mike (Austria)]

Quote:Who else has machines to test? Maybe a pattern will emerge, but it seems this behavior was not at all consistent across various model lines.

Well lacking a physical collection, various microcode emulators (my revived goXX apps, Nonpareil, Sydney Smith's online emulators, and Teenix Multicalc) will have to suffice.

Discounting changes dictated by the calculator model (absence of / numerical / alpha labels) my test program looks like
LBL A ; 1 ; RTN ; LBL B ; 2 ; RTN ; LBL C ; 3 ; RTN ; LBL D ; 4 ; RTN

With one exception, all models that I could test behave either of the following ways, no matter how the program is started ( GTO xx ; R/S vs. GSB xx or XEQ xx ):
RTN resets to step 0: 34c, 11c, 15c, 16c, 32sii (physical)
RTN stops at next step: 29c, 67, 33c, 41c(vx), 42s

As expected the comparison confirms that 29c and 67 are close relatives, and the 41 and 42 were designed to make 67 users feel at home. The 33c has subroutines but no labels. The 15c (along with the other 1xc models) cannot deny its 34c heritage. In all tested emulators, RTN executed from the keyboard in run mode resets to step 0.

So far for the boring stuff. For a little surprise we need to go back to the beginning. When above program is entered into the 65, behavior depends on how you start the program. Hit any of the A-D keys, and execution stops at RTN as expected (e.g. A -> 1). However, when execution is started with R/S, the first RTN is ignored, and the program stops only at the next RTN (e.g.: GTO A ; R/S -> 2). I did not find mention of this anomaly in the 65 manual, which on page 62 states,

"The RTN at the end of the program stops calculator execution, halts the stepping of the program pointer, and returns control to the keyboard"

Yet another example for the pleasure of playing with old calculator models. Thanks Bob for the suggestion. Maybe someone with a physical 65 wants to verify this?

Best, Mike