Yet another post asking how to change the radix (period or comma for "decimal point") on a Voyager-series model has been posted. It's undoubtedly the #1 FAQ, which may have prompted the "deleted" response that I surmise was somewhat gruff.
On the Spice models (e.g., HP-34C), changing the radix required changing an internal jumper in the calculator. The radix never changes accidentally (due to dead or removed battery, for example), but required HP to be careful which units to ship to a given market...
The HP-41 radix mode is set by changing flag 28. 1000's-separator mode (present or absent) is set by changing flag 29. This isn't exactly intuitive, but it allows extra flexibility in programs. There seem to be few complaints about wrong modes; perhaps these don't get changed accidentally...
The Voyager series (e.g., HP-11C) radix mode is set by holding down the "." key while turning the calculator on. This is a very simple, intuitive procedure, once it is learned from the manual. It also saved a valuable keyboard position for a function that is rarely, if ever needed by most users. That's not to say a user might not want to switch occasionally, though: If a foreign math/science/engineering book with numbers were being read, the user could make the numbers displayed on his calc match those in the text.
Apparently, there were complaints from users not knowing how to fix their undesired radix mode on their Voyager-series models. So, all of the successor Pioneer-series models included radix-setting functions that are accessible during operation. Examples: "RDX," (HP-42S); "RADIX," (HP-32S/SII); "./," (HP-20S); "." and "," (HP-17B/BII). These commands are generally keystroke-programmable, as well (if there's a need for it).
The original RPL-based HP-28 and HP-48 don't separate 1000's, for whatever reason...
-- KS
Edited: 8 Sept 2006, 10:49 p.m. after one or more responses were posted