I used to be able to do this for z80. I owned a spectrum and the user manual had a list of z80 instructions together with their byte code. Lacking an assembler,

I used to be able to do this for z80. I owned a spectrum and the user manual had a list of z80 instructions together with their byte code. Lacking an assembler, my only way of writing code was to hand write the numbers and then POKE them into memory. Ah, all those wasted hours writing code, only for it to instantly crash and lose everything...