Assembly language: The fifth Chapter [BX] and loop instructions

1.[BX] and memory unit

[BX] refers to the segment address in the DS, offset address in BX in the memory unit

2.loop

Used to describe loops

3. We define the descriptive symbol "()"

Register: (ax/al) represents the contents of the Ax/al register

Segment Register: ((DS) *16+ (BX)) indicates that the segment address is DS content, and the contents of the memory unit with the offset address of BX content

Memory Unit: (20000H) represents the contents of a 20000H memory unit

4. Convention symbol Idata represents a constant

mov ax,idata means mov ax,1 mov ax,2 etc.

mov ax,[idata] means mov ax,[1] mov ax,[2] etc.

Segment register machine is not available in this way MOV

5.1[BX]

mov Ax,[bx] The DS content as the segment address, BX content as the offset address of the 2 memory unit content into Microsoft Dynamics AX

mov [bx],ax put ax content into DS content as segment address, BX content as an offset address in 2 memory units

5.2 Loop Command

Format: Loop label

Loop execution steps: 1. (CX) = (CX)-1 2. Determine CX, not 0 go to the label position to execute

Example: Calculate 2 of the 12-time Square

Assume Cs:code

Code segment

MOV ax,2

MOV cx,11

S:add Ax,ax

Loop s

Code ends

End

5.3 Tracking the Loop command with debug

Debug 1.exe

-R

-T

-T

..

-P (int 21H is performed with P)

1. If you want to jump directly to the cs:xx position, execute with-G XX

2. If you want to jump in the loop, that is, stop waiting for-t after the loop, use the-p command

5.4 Debug and assembler compiler for different processing of instructions

Same instruction:

MOV ax,[0] In debug means to put ds:0 and Ds:1 memory unit contents into AX

In the MASM equals the mob ax,0

How to troubleshoot assembly source problems:

1. mov bx,0 mov ax,[bx]

2. mov Ax,ds:[0]

Combined application of 5.5 loop and [BX]

Assembly language: The fifth Chapter [BX] and loop instructions