One can write a string copy routine using two instructions, assuming that the source and destination are already in registers.
loop: MOVB (src)+, (dst)+
BNE loop
The routine takes full advantage of the fact that MOV updates the processor flag. The loop will continue until the value at the source address is zero, at which point the branch will fall through to the next instruction. This is why C strings are terminated with zeros.
Snippet from "https://dave.cheney.net/2017/12/04/what-have-we-learned-from...":
One can write a string copy routine using two instructions, assuming that the source and destination are already in registers.
The routine takes full advantage of the fact that MOV updates the processor flag. The loop will continue until the value at the source address is zero, at which point the branch will fall through to the next instruction. This is why C strings are terminated with zeros.