Assembly Language Learning Notes (eight) two basic problems in data processing

1.bx,si,di,bp
Use: Reg to represent registers, Sreg to represent segment registers
Reg:ax,bx,cx,dx,ah,al,bh,bl,ch,cl,dh,cl,sp,bp,si,di
Sreg:ds,ss,cs,es
Only four registers in 8086 can be placed in the middle of [] as a memory unit addressing
BP and Bx, Si and di are not combinable, and the rest can be
BP: As long as the use of BP in [], and no display of the given segment address, the segment address is the default in the SS
DS->BX (default)
SS->BP (default) but you can force the display to give

assembly language Expression Data location:
1. Instantly count Idata mov ax,1
2. Register mov AX,BX
3. Segment address and offset address mov ax,[bx]/[bp]

2. How long does the instruction process data
In the machine instruction, indicate whether the instruction is a word operation or a byte operation.
1. Specify the size of the data to be processed by the register name: Ax:16;al:8 bit
2. If no register name exists, use: Word ptr or byte ptr
3. Other methods: Some directives default on whether to access their own units or their own units
Push, pop: operate on words only

3.DIV Instruction: Division.
Divisor: 8-bit or 16-bit, in register or memory unit
Divisor: Default in AX or DX and ax
When the divisor is 8 bits, the divisor is 16 bits (AX)
When the divisor is 16 bits, the divisor is 32 bits (DX+AX)
Results: Operation 8 bits, quotient in AL, remainder in AH
Operations 16 bits, quotient in ax, remainder in DX
div byte ptr ds:[0]
Meaning:
(a1) = (Ax)/((DS) *16+0)
(AH) = remainder of (AX)/((DS) *16+0)
div Word prt es:[0]
Meaning: *10000h is represented by multiplying by a 16-bit, four 0000 representing a 16-bit
(AX) =[(DX) *10000h+ (AX)]//((DS) *16+0)
remainder of (DX) =[(DX) *10000h+ (AX)]//((DS) *16+0)

4. Pseudo-directive: Dd:dword
Double Word dual-font data
Db
DW can be accommodated with a DW as long as it is not more than 2^16
Dd

5.dup operator: In assembly language, the same as DB, DW, DD, etc., also has the compiler to recognize the processing of matching
DUP repeat
DB 3 dup (0): 3 bytes defined, their values are 0, equivalent to db0,0,0
DB 3 dup (0,1): 6 bytes defined, equivalent to DB 0,1,0,1