I know that addition of two unsigned integers larger than the bus size of a given processor can be achieved via the carry flag. And normally, the same is true for signed integers using the overflow...

In the flag register of Z80, 8080, 8085, and 8086 processors, what is the purpose of bits 1, 3, 5, which are documented as "reserved" or "undefined"?

I get the point of MOV, STA and LDA instructions, but what I don't understand is why are there three different instructions for two different processes? STA is for copying data from accumulator t...