In the beginning was CAOS (1988)

It also stands for "Cassette Aided Operation System" - in the GDR. It was used for East Germany's 8 bit computers (KC85 line).

Even as an East German pupil, the physics teacher in my school who started a "computer club" got us ZX Spectrum, C64, C128 and 8 bit Atari. I got to use and later own GDR-made KC85 elsewhere. Having used both, for 8 bit machines the KC85, especially the last model KC85/4, was really good - for work (no way to beat the game abilities and huge amount of software of the C64).

I still remember how you told "CAOS" about software loaded into the computer: You had 7F7F (7F is LD A,A in assembler if I remember correctly, so unlikely to be found in any code) followed by a string used as name for the software followed by either 00 or 01, I don't quite remember, I think two values existed which lead to two different uses of the name. The program started in the next byte. CAOS would search the RAM for /F/F and display the names in a menu. You select the program you want to start and it jumps there. Software was soooo much simpler. To call an OS routine you put a number into register A and called a fixed memory address. You pretty much knew every single byte of the 64K RAM personally.

I only had a DIS-assembler - which I found in a printed computer magazine and manually entered as HEX code before being able to save it to cassette for later repeat use. To write assembler code, I wrote it all on paper. Then I used a booklet of assembler codes for the Z80 clone U880 CPU to manually convert it into HEX code. I had to do a bit of binary arithmetic especially for relative jumps backwards. Then I used a hex editor to enter the code and used my dis-assembler to check if I had translated it all correctly. Ah, good times.

There were radio broadcasts of software, which you could record to cassette and then read into the KC86 computer. It was actually fairly easy to tell just from the sound if a piece of software was written in BASIC or in Assembler.

I played a bit on a friend's Amiga but in the end got an Atari 1040ST with 70Hz B/W monitor, which for screen work was far superior to the 50Hz of the Amiga. Only black and white though, still, enough for work.

https://de.wikipedia.org/wiki/Cassette_Aided_Operation_Syste...

https://en.wikipedia.org/wiki/KC_85

http://www.mpm-kc85.de/html/CAOS_42.htm

https://en.wikipedia.org/wiki/U880