>>>>LDIR? ;-)
>>>>Fortran
>>>
>>>LOL, LDIR was a Z80 ASM block memory command. Old inside joke.
>>
>>Yup, one of those where that look like a word but a completely wrong one. BCPY or BTRN would be meaningful. Not a theoretical chance that I'd remember what abbreviates to LDIR.
>>
>>I once wrote my own printer driver for ZX... ok, copied what was there, and reworked it from ZX's thermal printer to Seikosha's 7-dot matrix printer. It even worked with COPY command - which was the best misnomer ever :). And it still fit into the 256 byte printer buffer.
>
>[well, it's Sunday, I'll assume the permission to keep off-topic in most western countries]
>
>Dragan, Load, Increment and Repeat, if I recall it correctly. My first work in computers: I was my brother's assembler (get his Z80 instructions, change them into binary form, and poke the bytes inside a REM in the first line of the ZX BASIC program). Convergently, I also wrote a dot-matrix printer and even get paid for that (a brand new Sinclair QL computer).
>
>From those days, my favorite Z80 instruction: DJNZ (although hard to get it right at first - lots of resets because of this little bugger).
>
>And a recommendation, for those machine coder programmers at heart: https://en.wikipedia.org/wiki/Human_Resource_Machine (interesting puzzles to solve by using a tiny assembly language).

Those were the days. I learned the whole Z80 instruction set from my head including the use of the interrupt registers.
I too build a routine to print on a MSX printer. One for printing out photos by dithering the pixels.

DJNZ ... from the top of my head. The NZ means non-zero, I guess for the A register value. The DJ must be a jump although I can't rember the difference with JPNZ ?

Oh. man this is so long ago, it brings back fond memories of trying to fit a program in 4 or 8K.

My favourate command was LDIR where you could create patterns of values by having overlapping source and destination (HL and DE registers). Much later I used that same principle in VFP with the ACOPY command.

Good memories.