Lab 2 - mul, div, add, sub

mov al, [a] ;al=22
mov al, [b] 
mov ax, [b] ;ax=1234
mov ax, [a]
mov eax, [b] ;eax=22_0A_12_34
mov ax, [a+1] ;a+1=b=1234
mov bx, [c-2] ;b=12_34

res instructions

reserves memory

resb - byte resw - word resd - double resq - quad rest - tetra - 10 bytes

Example

c resd 3 reserves $4\times 3=12\text{ bytes}$ (double type reserved 3 times)

a db 22h
b db 22h
c dw 2h
d dw 10h
 
mov ax, [a];ax=22_22
mov bx, 4;bx=00_04
add bx, ax;bx=22_26
mov ax, [b+1];ax=00_02
add ax, [c+1];ax=10_02
mov [c], ax

What value will be in AX register after running the following code, if variable a is a word, b and c are bytes and a=5, b=9, c=4

; 05 00 09 04
;   a    b  c 
mov ax, [a] ;ax=00 05
add ax, 20  ;ax=00 19
mov bx, [b] ;bx=04 09
mov bh, 0   ;bx= 00 09
mov [b], b  ;00 09, [b]=bx
add bx, [c] ;

mul instructions

b*b=>w AX=AL*Y w*w=>dwDX:AX=AX*Y dw*dw=>qw EDX:EAX=EAX*Y

div instructions

div Y y-byte ax:y=>AL,AH y-word
(DX:AX):y=DX,AX (Quotient & Remainder)

a dw 1
b dw 13
mov ax, [a]
mul [b]
--------
DX:AX

a dw 7
b dd 9
mov EAX, 0
mov AX, [a]
mul [b]

a db 8
b dw 40 h
mov AX, [b]
div [a] ;AH=00, AL=05

• 📅 2024-10-14 Homework Lab 2 (don’t open parantheses, homework on computer, look at theory&examples (~vancea) n&n+15 from every problem set, 2&17 from the sets)