5. MUL Example

• The MUL instruction sets the Carry and Overflow flags if the upper half of the product is not equal to zero.

• The Carry flag CF is normally used for unsigned arithmetic.

• For example,

  • when AX is multiplied by a l6-bit operand, the product is stored in DX:AX.

  • If DX is not equal to zero, the Carry flag is set.

• To multiply

      0l00h × 2000h
  

  we could use the following fragment:

      .DATA
      one WORD 2000h
      two WORD 0100h
      .CODE
      mov ax, [one]
      mul [two] ; CF = 1, producing 0020h:0000h in DX:AX