HP-25 Subroutines possible?

[PANAMATIK]

(06-24-2017 12:51 PM)Dave Britten Wrote:  ... I'm not sure how tight the 25 ROM is, but the added instructions would only have to push a return address, then jump to the appropriate GTO routine. RTN would just pop an address, and GTO. You'd probably need one extra register to hold the return stack and a stack pointer.

Very very tight! No byte left. Here is the HP-25 ROM Code

Bernhard