20. XCHG Instruction, Exchanging Integers

• The XCHG (exchange data) instruction exchanges the contents of two operands.

• There are three variants:

      XCHG reg, reg
      XCHG reg, mem
      XCHG mem, reg
  

• You can exchange data between registers or between registers and memory, but not from memory to memory:

          xchg    ax, bx       ; Put AX in BX and BX in AX
          xchg    memory, ax   ; Put "memory" in AX and AX in "memory"
          xchg    mem1, mem2   ; Illegal, can't exchange memory locations!
  

• The rules for operands in the XCHG instruction are the same as those for the MOV instruction...

  • ...except that XCHG does not accept immediate operands.