The HP-25 was introduced as the successor to the HP-45 and HP-55 calculators. Initially, it dod not have continuous memory and so cleared memory when it was switched off, but the HP-25C did have continuous memory.
The HP-25 built on the HP-55's programming capability, and while it could hold 50 steps of program, this was better than the HP-55, which could only record 50 keystrokes.
The HP-25 was the first mid-range programable calculator from HP, and started a long line of these calculators, finishing with the HP-33S (from the surveyors' viewpoint).
While we have a number of program for the HP-25, we don't have them as PDFs yet, but they will appear over time, if only for historical interest.