I've written about seven programs for my HP 12c. I've manually combined them into a big "multiprogram" which starts with a jump table: a bunch of GTO commands, each one jumping to the entry point of one of the actual programs. The reason for that is that the HP 12c has only one contiguous program area. Fortunately, the calculator allows you to manually execute a GTO command before pressing R/S to start the execution. But instead of having to remember the starting address of each program, I just put them on the GTO instructions on the jump table so I just need to manually do GTO 003 and press R/S to start the third program, because address 003 has the GTO to the starting point of the third program.
But managing this multiprogram is very tedious. When a program is placed in a different starting address in memory, all the GTO targets of that program need to be updated and offset correctly to continue working. So I made a program called Voyager Manager that lets me compile any number of programs into one such multiprogram, taking care of the GTOs and the jump table automatically. It works for my programs but it's still a very early version. It comes with GNU/GPLv3 source code, Lua binaries for Windows included, and a library that includes my programs for the HP 12c to get you started.
You can download Voyager Manager from here.
