The Computer is programmed with simple numbers for adding, running loops and so on, but it's not possible to program the cpu directly.
Chriz tells us :
I own a kosmos cp1 and it's still functioning. It has a very good manual which is kind of a machine language course for the cp1-inctructions. The cpu was a 8049 (8bit) with 2048 byte rom and 128 byte ram integrated (6 Mhz) and the memory+io chip a 8155 with 256 byte ram and 22 bit io. The 256 byte of 8155 ram give you 128 storage cells for the cp1-instructions (like 04.056 which means load absolute 56 into accumulator).
You could control electronics and fishertechnik with this little computer, even model trains. There was an io-interface (8 relays, 8 inputs), a cassette interface for loading and saving programs, an extension interface (another 8155 gives you +128 storage cells and 16 ios) and another io-interface with 8 leds and transistor drivers.
"Little is known about this german training kit..." may have been true when the article was written, but by now, quite a bit of information has surfaced: - There are some excellent pictures, including all the expansions, at http://www.8bit-homecomputermuseum.at/computer/kosmos_computer_praxis_cp1.html (as TOM already pointed out) - The full set of manuals (including all expansions, in German) is available at https://www.retrozone.ch/cp1/ - Michael Mustun provided a ROM disassembly at https://www.flagsoft.com/cmswp/de/software/kosmos-cp-1-computer-praxis/
My experience is similar - actually, I got more into the hardware side. Actually, I built a cassette interface of my own, since the original one was too expensive for me at that time. Along with a little 'modding' of the CP-1. And it still works, like the whole machine. Anyone interested in the schematics of my home-built cassette interface, might contact me at: stargar at gmx dot de. Did anyone do further modding, acceleration, enhancements/improvements to the code, or manage to get anything useful attached to the system bus, besides the RAM extension? I have not yet given up the idea of cloning the whole machine to a nifty little box and have it control something in the house. I also wrote an enhanced version of the 'Towers of Hanoi' robot control program, which is capable of moving a tower of maximum 11 slices (with the RAM extension only), if someone might be interested. (Heck, I could make it into a *.wav file, probably an *.mp3 to get it loaded... don't know actually if the file is compatible with the original cassette interface.)