Assembly: Registers and Status Flags

The CPU's tiny workbench.

Registers are the CPU's fastest storage. Instructions typically load a value into a register, operate on it, then store the result.

A status register holds flags set by operations: zero (result was 0), carry (an addition overflowed), and negative. Conditional jumps read these flags to make decisions.

Learning flags explains how a C if statement becomes machine code.

; generic teaching syntax
        LOAD  R0, 10
        SUB   R0, 10     ; result is 0, so the zero flag is set
        JZ    done       ; jump taken because zero flag is set
        ...
done:   HALT