Question

. Write a sequence of instructions to compute the following arithmetic expression and store the result in register DX: 7 + (-20) * 14 - (-10) * 8– 9

Trace the contents of registers, assume initial contents are 0000

Instruction	AX	BX	CX	DX	Remark
initial	0000	0000	0000	0000

Answer 1

The sequence of instructions are as follows:

1.MOV AX,-20
2. MUL AX,14
3. MOV BX,-10
4. MUL BX,8
5. MOV CX,9
6. SUB AX,BX
7. SUB AX,CX
8. MOV DX,7
9. ADD DX,AX

The content of registers are shown as below:

Instruction	AX	BX	CX	DX	Remark
Initial	0	0	0	0
MOV AX,-20	-20	0	0	0	Move -20 to Register AX
MUL AX,14	-280	0	0	0	Multiply 14 to Register AX
MOV BX,-10	-280	-10	0	0	Move -10 to Register BX
MUL BX,8	-280	-80	0	0	Multiply 8 to Register BX
MOV CX,9	-280	-80	9	0	Move 9 to Register CX
SUB AX,BX	-200	-80	9	0	Subtract BX from AX and store the result in AX
SUB AX,CX	-209	-80	9	0	Subtract CX from AX and store the result in AX
MOV DX,7	-209	-80	9	7	Move 7 to Register DX
ADD DX,AX	-209	-80	9	-202	Add DX and AX and store the result in DX