HP-25 purpose

[Steve Simpkin]

Matt, To more directly answer your question. It appears that the HP-25 was originally intended to be a low cost replacement for the HP-45 with more memory registers. It was allocated 2k words of ROM, the same amount as used in the HP-45. Due to improvements in the new ACT chip and the incredible talents of people like Randall B. Neff, they managed to include the main features of the HP-45 and add programmability using just 2k words of ROM. There simply was no room to add features like a looping counter and subroutines. This is all the more amazing since the HP-55 required 3k words of ROM to achieve a similar capability. It would take HP another 2 years to add looping, subroutines and a few more features to the Woodstock family with the HP-29C/19C models. And that required 4k words of ROM.
https://www.hpmuseum.org/cgi-bin/compare...ON&diff=ON