一 MVC指令
1．移动字符串指令MVC
移动字符串指令MVC的格式为：
MVC D1(L,B1),D2(B2) (移动字符串)
功能：（D1+（B1）） ← （D2+（B2））
L个字符
指令的执行用开始于D2(B2)的L字节替换开始于D1(B1)的L字节的内容。L个字节的内容
每次改变一个，从左边开始。如果域不重叠的话，这一事实是不重要的，但当域重叠时就特
别重要。本指令的操作码为D2。指令执行不改变条件代码CC。
例如指令：
MVC 14(8,R12),0(R1)
产生编码D207 C00E 1000。
SS语句可以使用隐式地址。这里，正如RS和SI指令中的情形一样，隐式地址中不说明
变址寄存器。当用一个隐式地址说明第一个操作数时，通过将其放在第一个操作数括号中说
明长度。这是一个可能产生混淆的地方。例如，指令：
MVC FIELD1(15),FIRLD2
说明操作数的长度为15，第一个操作数的地址为FIELD1，而不是R15内容的偏移。SS指令
中的长度说明允许为0，如果这样做了，生成的长度代码为0
二 汇编EXAMPLE
cobol
data segment
org 80h
psp dw 0ffh dup(?)
ddd db 'diretory:$'
head db 'name size type date time ',0dh,0ah,24h
space db ' ',24h
dir db 'xxx <dir> ',24h
fn db 200h dup(?)
dta db 128 dup(?)
msg db 'press any key to continue...',0dh,0ah,24h
newline db 0dh,0ah,24h
count db ?
show db 0
base_10 dw 10
used_32bits_high dw 0
used_32bits_low dw 0
var_32bits_high dw 0
var_32bits_low dw 0
quotidient_32bits_high dw 0
quotidient_32bits_low dw 0
negate_mask equ 0FFFFh
lowest_signed_32bits_high dw 8000h
lowest_signed_32bits_low dw 0000h
lowest_signed_32bits_string db '-2147483648$'
qhigh dw 0
rhigh dw 0
qlow dw 0
rlow dw 0
qhigh_redundant dw 0
rhigh_redundant dw 0
q_0 dw 0
qhigh0 equ 0h
rhigh0 equ 0h
qhigh1 equ 1999h
rhigh1 equ 6h
qhigh2 equ 3333h
rhigh2 equ 2h
qhigh3 equ 4CCCh
rhigh3 equ 8h
qhigh4 equ 6666h
rhigh4 equ 4h
qhigh5 equ 8000h
rhigh5 equ 0h
qhigh6 equ 9999h
rhigh6 equ 6h
qhigh7 equ 0B333h
rhigh7 equ 2h
qhigh8 equ 0CCCCh
rhigh8 equ 8h
qhigh9 equ 0E666h
rhigh9 equ 4h
filenum db 0
dirnum db 0
filespace db ' File(s) $'
dirspace db ' Dir(s) $'
bytes db ' Bytes.',0dh,0ah,24h
bytesfree db ' Bytes free.',0dh,0ah,24h
data ends
stack1 segment stack
dw 0ffh dup(0)
stack1 ends
main segment
assume cs:main,ds:data,ss:stack1
org 100h
cmdln equ byte ptr es:[82h] ;command line data
;-------------------------------------------------------------------------------
p1 proc near
push ds
mov ax,data
mov ds,ax
pop psp
mov es,psp
mov ax,stack1
mov ss,ax
mov cl,byte ptr es:[80h]
cmp cl,0 ;command line?
jne l4 ;yes
no_dir:
mov ah,19h ;no
int 21h
add al,'a'
mov byte ptr[fn],al
mov word ptr[fn+1],5c3ah
mov ah,47h ;current directory but no driver,so have to
lea si,fn[3] ;use 19h to add myself
sub al,'a'
mov dl,al
int 21h
lea di,fn[3] ;to point di to the end of the diretory
l7:
mov al,[di]
cmp al,0
je l6
inc di
jmp l7
l4:
lea si,cmdln
lea di,fn
cld
xor ch,ch
dec cl
;rep movsb
lea di,fn
lea bx,cmdln
lea bp,fn
repeat:
mov al,es:[bx]
mov ds:[bp],al
inc bx
inc bp
inc di
dec cl
jnz repeat
l6:
mov cl,[di-1] ;end by '\' ?
cmp cl,92 ;92-->'\'
je l8 ;yes
;mov byte ptr[di],92 ;no
;inc di
cmp byte ptr[di-1],'W'
jne notW
mov al,1
mov [show],al
notW:
cmp byte ptr[di-1],92 ;'\'
je l8
dec di
jz no_dir
jmp notW
l8:
mov word ptr[di],0a0dh ;end by $ for printing
mov byte ptr[di+2],24h
mov ah,09h ;print "directory:*:\*\*\"
;lea dx,ddd
mov dx,offset ddd
int 21h
mov ah,09h
lea dx,fn
int 21h
mov ah,09h
mov al,[show]
cmp al,1
je w_head
lea dx,head
int 21h
w_head:
mov word ptr[di],2e2ah ;add '*.* ' at the end
mov word ptr[di+2],002ah
l5:
lea dx,dta
mov ah,1ah
int 21h
mov ah,4eh ;first fdt matched
mov cx,16h ;all file
lea dx,fn
int 21h
call outp ;print first file imformation
mov cl,1
mov count,cl
;-------------
;mov ah,4ch
;int 21h
;-----------
l2:
mov ah,4fh ;next fdt
int 21h
jc l0 ;end when no file any more
call outp ;print next file imformation
mov cl,count
inc cl
mov count,cl
cmp cl,14h
ja pause
pause_end:
jmp l2
pause:
mov dl,[show]
cmp dl,1
je pause_end
mov ah,9h;move 9 into ah (9 is the interrupt for output)
lea dx,msg;move the message into dx
int 21h ;call dos function
mov ah,7h;move 7 into ah (7 is the interrupt for input)
mov dx,00h;get the actual input
int 21h ;dos interrupt
mov cl,0
mov count,cl
jmp pause_end
l0: ;int 20h ;end
mov dl,[show]
cmp dl,0
je not_newline
mov ah,2 ;new line
mov dl,0dh
int 21h
mov ah,2
mov dl,0ah
int 21h
not_newline:
lea dx,[space]
mov ah,09h
int 21h
mov al,[filenum]
xor ah,ah
mov [var_32bits_low],ax
xor al,al
mov [var_32bits_high],ax
call showspace
lea dx,filespace
mov ah,09h
int 21h
mov ax,[used_32bits_high]
mov [var_32bits_high],ax
mov ax,[used_32bits_low]
mov [var_32bits_low],ax
call showspace
lea dx,bytes
mov ah,09h
int 21h
lea dx,[space]
mov ah,09h
int 21h
mov al,[dirnum]
xor ah,ah
mov [var_32bits_low],ax
xor al,al
mov [var_32bits_high],ax
call showspace
lea dx,[dirspace]
mov ah,09h
int 21h
;-----------------------get free space
mov dl,fn[0]
sub dl,'a'
mov ah,36h
int 21h
mul bx
mov bx,cx
xor cx,cx
call mymul32
mov var_32bits_high,cx
mov [var_32bits_low],bx
call showspace
lea dx,bytesfree
mov ah,09h
int 21h
mov ah,4ch
int 21h
p1 endp
pspace proc near
push dx
push ax
mov dl, ' '
mov ah, 2h
int 21h
pop ax
pop dx
pspace endp
printax proc near
cmp ax,0
je pret
push bx
push cx
push ax
push dx
xor cx,cx
;jmp lable1
b11: xor dx,dx
lable1: mov si,10
div si
push dx
inc cx
cmp ax,0
jne b11
b22: pop dx
add dl,30h
mov ah,2
int 21h
loop b22
pop dx
pop ax
pop cx
pop bx
pret: ret
printax endp
printax_hex proc near
mov cx,4 ; print 4 hex digits (= 16 bits)
.print_digit:
rol ax,4 ; move the currently left-most digit into the least significant 4 bits
mov dl,al
and dl,0Fh ; isolate the hex digit we want to print
add dl,'0' ; and convert it into a character..
cmp dl,'9' ; ...
jbe .ok ; ...
add dl,7 ; ... (for 'A'..'F')
.ok: ; ...
push ax ; save EAX on the stack temporarily
mov ah,2 ; INT 21H / AH=2: write character to stdout
int 21h
pop ax ; restore EAX
loop .print_digit
ret
printax_hex endp
;----------------------------print the file imfomation--------------------
outp proc near
push bx
push dx
push ax
push cx
mov cx,16
lea bx,dta[1eh] ;print name
o0:
mov dl,[bx]
cmp dl,0
je o1
mov ah,2
int 21h
dec cx
inc bx
jmp o0
o1:
mov ah,02h ;print space between name and size
mov dl,20h
int 21h
loop o1
call b2d ;print size and dir type
;----judge is W
mov dl,[show]
cmp dl,1
je w_file
call datm ;print date and time
mov ah,2 ;new line
mov dl,0dh
int 21h
mov ah,2
mov dl,0ah
int 21h
w_file:
pop cx
pop ax
pop dx
pop bx
ret
outp endp
;------------------------------print size-------------------------------------
b2d proc near
push cx
push ax
push dx
push si
xor cx,cx
lea si,dta[1ah]
mov ax,[si]
call add_used_space
call add_filenum
cmp ax,0
je b4
;----judge is W
mov dl,[show]
cmp dl,1
je b5
xor cx,cx
b1:
xor dx,dx
mov si,10
div si
push dx
inc cx
cmp ax,0
jne b1
mov si,cx
b2:
pop dx
add dl,30h
mov ah,2
int 21h
loop b2
mov cx,10
sub cx,si
b3:
mov ah,02h
mov dl,20h
int 21h
loop b3
;----judge is W
mov dl,[show]
cmp dl,1
je b5
mov ah,9
lea dx,space
int 21h
jmp b5
b4:
call add_dirnum
call sub_filenum
;----judge is W
mov dl,[show]
cmp dl,1
je b5
mov ah,09h
lea dx,dir
int 21h
b5:
pop si
pop dx
pop ax
pop cx
ret
b2d endp
add_filenum proc near
push ax
mov al,[filenum]
inc al
mov [filenum],al
pop ax
ret
add_filenum endp
add_dirnum proc near
push ax
mov al,[dirnum]
inc al
mov [dirnum],al
pop ax
ret
add_dirnum endp
sub_filenum proc near
push ax
mov al,[filenum]
dec al
mov [filenum],al
pop ax
ret
sub_filenum endp
;------------------------------print date and time-----------------------------------------------
datm proc near
push ax
push bx
push cx
push dx
push di
lea bx,dta[18h];data
mov di,[bx]
mov cx,7;year
xor bx,bx
d1:
shl di,1
rcl bx,1
loop d1
add bx,1980
call bi2de
mov ah,2
mov dl,"."
int 21h
mov cx,4;month
xor bx,bx
d2:
shl di,1
rcl bx,1
loop d2
call bi2de
mov ah,2
mov dl,"."
int 21h
mov cx,5;day
xor bx,bx
d3:
shl di,1
rcl bx,1
loop d3
call bi2de
mov cx,3
d7:
mov ah,2
mov dl," "
int 21h
loop d7
;time
lea bx,dta[16h]
mov di,[bx]
mov cx,5;hour
xor bx,bx
d5:
shl di,1
rcl bx,1
loop d5
call bi2de
mov ah,2
mov dl,":"
int 21h
mov cx,6;min
xor bx,bx
d6:
shl di,1
rcl bx,1
loop d6
call bi2de
pop di
pop dx
pop cx
pop bx
pop ax
ret
datm endp
;---------------------------------binary2decimal-----------------------------
bi2de proc near
push ax
cmp bx,9
ja bi0
mov ah,2
mov dl,'0'
int 21h
bi0:
xor cx,cx
mov ax,bx
bi1:
xor dx,dx
mov si,10
div si
push dx
inc cx
cmp ax,0
jne bi1
bi2:
pop dx
add dl,30h
mov ah,2
int 21h
loop bi2
pop ax
ret
bi2de endp
;----------------multiplies dx:ax x cx:bx return dx:ax:cx:bx
mymul32 proc near
push si
push di
mov si,dx ;save op1hi in si
mov di,ax ;save op1lo in di
mul bx ;op1l0 x op2lo
push ax ;save 1st (32 bit) pp. on stack
push dx
;
mov ax,si ;op1hi in ax
mul bx ;op1hi x op2l0
pop bx ;add 2nd (48 bit) pp. to pp1
add ax,bx
adc dx,0
push ax
mov bx,dx ;pp1 + pp2 in bx:tos:tos+2
;
mov ax,di ;op1lo in ax
mul cx ;op1lo x op2hi
pop di ;add 3rd (48 bit) pp. to pp1 + pp2
add di,ax
push di
mov di,0
adc bx,dx
adc di,0 ;pp1+pp2+pp3 in di:bx:tos:tos+2
;
mov ax,si ;op1hi in ax
mul cx ;op1hi x op2hi
add ax,bx ;add 4th (64 bit) pp. to pp1+pp2+pp3
adc dx,di
pop cx
pop bx ;final product in dx:ax:cx:bx
;
pop di
pop si
ret
mymul32 endp
showspace proc near
push ax
push bx
push dx
push cx
mov ax,0
mov bx,0 ;bx: quotidient_32bits_high
mov dx,0 ;dx: quotidient_32bits_low
mov cx,0 ;counter = 0
;16bits or 32bits ?
mov ax,var_32bits_high
cmp ax,0
jne _32bits_routine
jmp _16bits_routine
;;;
_32bits_routine:
mov cx,0
;if == -2147483648 (-2^31)
mov ax,var_32bits_high
cmp ax,lowest_signed_32bits_high
jne check_if_neg
mov ax,var_32bits_low
cmp ax,lowest_signed_32bits_low
jne check_if_neg
;then
lea dx,lowest_signed_32bits_string
mov ah,9
int 21h
jmp return_to_dos
;if < 0
check_if_neg:
mov ax,var_32bits_high
cmp ax,0
jnl preparations
;then print "-" ...
mov ah,2
mov dl,'-'
int 21h
;... and negate number
;---------xor 0ffffffff , + 1----------
mov ax,var_32bits_high
xor ax,negate_mask
mov var_32bits_high,ax
mov ax,var_32bits_low
xor ax,negate_mask
inc ax
mov var_32bits_low,ax
jnc preparations
mov ax,var_32bits_high
inc ax
mov var_32bits_high,ax
preparations:
mov ax,var_32bits_high
mov quotidient_32bits_high,ax
mov ax,var_32bits_low
mov quotidient_32bits_low,ax
while_32bits:
; while >0 do
mov ax,quotidient_32bits_high
cmp ax,0
jne div_high_part
mov ax,quotidient_32bits_low
cmp ax,0
jne div_high_part
jmp print_char
div_high_part:
;divide high part
mov dx,0
mov ax,quotidient_32bits_high
div base_10
mov qhigh,ax
mov rhigh,dx
;case rhigh
mov ax,rhigh
cmp ax,0
je _rhigh0
cmp ax,1
je _rhigh1
cmp ax,2
je _rhigh2
cmp ax,3
je _rhigh3
cmp ax,4
je _rhigh4
cmp ax,5
je _rhigh5
cmp ax,6
je _rhigh6
cmp ax,7
je _rhigh7
cmp ax,8
je __rhigh8
cmp ax,9
je __rhigh9
_rhigh0:
mov ax,qhigh0
mov qhigh_redundant,ax
mov ax,rhigh0
mov rhigh_redundant,ax
jmp _aftercase
_rhigh1:
mov ax,qhigh1
mov qhigh_redundant,ax
mov ax,rhigh1
mov rhigh_redundant,ax
jmp _aftercase
__rhigh8:
jmp _rhigh8
__rhigh9:
jmp _rhigh9
_rhigh2:
mov ax,qhigh2
mov qhigh_redundant,ax
mov ax,rhigh2
mov rhigh_redundant,ax
jmp _aftercase
_rhigh3:
mov ax,qhigh3
mov qhigh_redundant,ax
mov ax,rhigh3
mov rhigh_redundant,ax
jmp _aftercase
_rhigh4:
mov ax,qhigh4
mov qhigh_redundant,ax
mov ax,rhigh4
mov rhigh_redundant,ax
jmp _aftercase
_rhigh5:
mov ax,qhigh5
mov qhigh_redundant,ax
mov ax,rhigh5
mov rhigh_redundant,ax
jmp _aftercase
_rhigh6:
mov ax,qhigh6
mov qhigh_redundant,ax
mov ax,rhigh6
mov rhigh_redundant,ax
jmp _aftercase
_rhigh7:
mov ax,qhigh7
mov qhigh_redundant,ax
mov ax,rhigh7
mov rhigh_redundant,ax
jmp _aftercase
_rhigh8:
mov ax,qhigh8
mov qhigh_redundant,ax
mov ax,rhigh8
mov rhigh_redundant,ax
jmp _aftercase
_rhigh9:
mov ax,qhigh9
mov qhigh_redundant,ax
mov ax,rhigh9
mov rhigh_redundant,ax
jmp _aftercase
_aftercase:
;divide low part
mov ax,0
mov q_0,ax
mov dx,0
mov ax,quotidient_32bits_low
div base_10
mov qlow,ax
mov rlow,dx
mov ax,rlow
add ax,rhigh_redundant
;if remainder >= 10
cmp ax,base_10
jl after_if
sub ax,base_10
mov dx,1
mov q_0,dx
after_if:
mov rlow,ax
mov ax,q_0
add ax,qlow
mov qlow,ax
jnc label1
mov ax,qhigh
inc ax
mov qhigh,ax
label1:
mov ax,qlow
add ax,qhigh_redundant
mov qlow,ax
jnc label2
mov ax,qhigh
inc ax
mov qhigh,ax
label2:
;push remainder to stack
mov ax,rlow
push ax
inc cx
mov ax,qhigh
mov quotidient_32bits_high,ax
mov ax,qlow
mov quotidient_32bits_low,ax
jmp while_32bits
;;;
_16bits_routine:
mov ax,var_32bits_low
mov bx,0 ;bx: quotient
mov cx,0
while_loop:
cmp ax,0
je print_char
mov dx,0
div base_10
mov bx,ax ;ax stores quotidient
mov ax,dx ;dx stores remainder
;push remainder
push ax
;counter = counter + 1
inc cx
;numerator = quotidient
mov ax,bx
jmp while_loop
print_char:
cmp cx,0
je return_to_dos
pop ax
;because at this point 0 <= ax <= 9, setting ah = 2 does not change the results
mov ah,2
mov dl,al
add dl,30h ;0-> '0',1->'1',....
int 21h
dec cx
jmp print_char
return_to_dos:
pop cx
pop dx
pop bx
pop ax
ret
showspace endp
;--------input:ax----------
add_used_space proc near
push ax
push bx
push cx
push dx
mov dx,[used_32bits_low]
add dx,ax
jnc add_finish
mov bx,[used_32bits_high]
inc bx
mov [used_32bits_high],bx
add_finish:
mov [used_32bits_low],dx
pop dx
pop cx
pop bx
pop ax
ret
add_used_space endp
main ends
end p1