数学表达式计算（汇编实现）

;#Mode=Dos
;Title:数学表达式计算
;Declare:仅支持 整数（0-65535），+，-，*，/，（）运算符
;Date:2012-11-15
;author:53101512 ZhongQiang
data segment
expression db 50,?,40 dup(0),'$';表达式数组
message db 50 dup('*'),0dh,0ah,'Please Input Expression:',0dh,0ah,'$';输入提示
message2 db 0dh,0ah,50 dup('*'),0dh,0ah,'The Answer is: ',0dh,0ah,'$';输出提示
top db 50 dup('*'),0dh,0ah,
'*','       Integer(0-65535),Support +,-,*,/,()      ','*',0dh,0ah,
'*','       example input    (45+32)/7-10            ','*',0dh,0ah,
'*','       Date:        2012-11-15                  ','*',0dh,0ah,
'*','       Id:          53101512                    ','*',0dh,0ah,
'*','       Name:        ZhongQiang                  ','*',0dh,0ah,
50 dup('*'),0dh,0ah,'$'
token db ?
arg db ?
result dw ? ;结果
nozero db 0 ;十进制输出辅助
data ends

code segment
assume cs:code, ds:data
start:
mov ax,data
mov ds,ax
;说明
lea dx,top
call printstring
;输入提示信息
lea dx,message
call printstring
;输入算数表达式
lea dx,expression
mov ah,0ah
int 21h
;表达式解析
lea si,expression
add si,2
mov al,[si]
inc si
mov [token],al
call exp
mov [result],dx
;输出提示及结果输出
lea dx,message2
call printstring
mov bx,result
call outputdec
;按任意键返回
mov ah,1
int 21h
;返回DOS
mov ah, 4ch
int 21h
exp proc
local temp:WORD ;定义局部变量
call term
mov temp,dx
while1:
cmp al,'+'
je add_
cmp al,'-'
je sub_

jmp end1
add_:
mov cl,'+'
mov [arg],cl
call match
call term
add temp,dx
jmp while1
sub_:
mov cl,'-'
mov [arg],cl
call match
call term
sub temp,dx
jmp while1
end1:
mov dx,temp
ret
exp endp

term proc
local temp:WORD ;定义局部变量
call factor
mov temp,dx
while2:
cmp al,'*'
je mul_
cmp al,'/'
je div_
jmp end_
mul_:
mov cl,'*'
mov [arg],cl
call match
call factor
mov cx,ax
mov ax,temp
mul dx
mov [temp],ax
mov ax,cx
jmp while2
div_:
mov cl,'/'
mov [arg],cl
call match
call factor
mov cx,ax
mov ax,temp
div dl
xor ah,ah
mov [temp],ax
mov ax,cx
jmp while2
end_:
mov dx,temp
ret
term endp
factor proc
local temp:WORD ;定义局部变量
cmp al,'('
je lef
xor cx,cx
mov cl,al
xor ax,ax
while3:
sub cl,'0'
mov BL,10
imul BL
add ax,cx
mov cl,[si]
inc si
cmp cl,'0'
jb end3
cmp cl,'9'
ja end3
jmp while3
lef:
mov cl,'('
mov [arg],cl
call match
call exp
mov temp,dx
mov cl,')'
mov [arg],cl
call match
jmp endx
end3:
mov dx,ax
dec si
mov al,[si]
inc si
ret
endx:
mov dx,temp
ret
factor endp
match proc
cmp al,arg
je true
true:
mov al,[si]
inc si
ret
match endp
;十进制输出子程序
outputdec proc
push cx
mov nozero,0
mov cx,10000
call main
mov cx,1000
call main
mov cx,100
call main
mov cx,10
call main
mov cx,1
call main
cmp nozero,0
jne ll
mov dl,30h
call printchar
ll:
pop cx
ret
main proc
mov ax,bx
mov dx,0
div cx
mov bx,dx
mov dl,al
cmp dl,0
jne ll1
cmp nozero,0
jne ll1
jmp ll2
ll1:
mov nozero,1
add dl,30h
call printchar
ll2:
ret
main endp
outputdec endp
;字符串输出子程序
printstring proc
mov ah,9
int 21h
ret
printstring endp
;字符输出子程序
printchar proc
mov ah,2
int 21h
ret
printchar endp
code ends
end start