HP-25 Subroutines possible?

[Matt Agajanian]

(06-20-2017 07:21 PM)PANAMATIK Wrote:  

(06-20-2017 06:16 PM)Matt Agajanian Wrote:  Given the tech advances from Classics to Woodstocks, would it have been possible to include three-levels of subroutine branching in the HP-25?

Theoretically yes, but I see three reasons why this was not possible.

First the ROM code of 2k instructions did not leave space for additional features like subroutines. It was squeezed until the last bit.

Second the HP-25 has only 49 program steps and for such small programs subroutines would not really have been an advantage with their overhead of LBL and RTN instructions.

Third, the development of the firmware with programmable subroutines was introduced with the HP-29C with 4k ROM code and 98 program steps, it was not finished when the HP-25 came into market.

Bernhard

Ah! Your second and third points make the case clear. But, given this second point, why does a 33E/C with its own three subroutine level/49 step program memory seem logical?