汇编中三个整数相减 (MASM)

Question

使用AddSub程序，编写一个仅使用16位寄存器减去三个整数的程序。插入call DumpRegs语句以显示寄存器值。

AddSub 示例程序：

TITLE Add and Subtract, Version 2 (AddSub2.asm)
; This program adds and subtracts 32-bit unsigned
; integers and stores the sum in a variable.
INCLUDE Irvine32.inc
.data
val1 DWORD 10000h
val2 DWORD 40000h
val3 DWORD 20000h
finalVal DWORD ?
.code
main PROC
mov eax,val1 ; start with 10000h
add eax,val2 ; add 40000h
sub eax,val3 ; subtract 20000h
mov finalVal,eax ; store the result (30000h)
call DumpRegs ; display the registers
exit
main ENDP
END main
How does it work? First,

Answer 1

如果不知道“addSub”程序，您可能只需要知道有符号整数（二进制补码）和 0-x 的操作码背后的理论。 (NEG)

八位示例，5-10-20

ldi a,5
ldi b,10
ldi c,20

neg b
neg c
addc a,b
addc a,c

可以吗？

Answer 2

问题是：以3.2节中的ADDSUB程序为参考，编写一个只对16位寄存器进行三个整数相减的程序。插入一个 cal DumpRegs 语句来显示寄存器值

工作是：

TITLE Add and Subtract      (AddSub.asm)

; Program Assignment 1 - Subtracting Three Integers   
; Using the AddSub program From Section 3.2 as a Reference,  
; Write a program that subtracts three Integer using only 16-bit     registers,  
; Insert a call DumpRegs statement to display the register values.

INCLUDE Irvine32.inc

 .code
 main PROC

 mov eax, 90000h    ;EAX = 10000h  
 sub eax, 40000h    ;EAX = 50000h   
 sub eax, 20000h    ;EAX = 30000h   
 call DumpRegs                ; display registers    

   exit    

   main ENDP   

   END main