Asm06第六讲课件.ppt

Chapter 2 REQUIREMENTS FOR USING PC SOFTWARE;ADDRESSING OF INSTRUCTIONS AND DATA Every instruction consist of at lest an operation (操作), such as move(数据传送), add. Depending on the operation, an instruction may also have one or more operands(操作数) that reference the data the operation is to process. An instruction can be addressed by CS:IP in code segment. For example: CS segment address: 0 5 B E 0H IP offset: + 0 0 2 3H Instruction address: 0 5 C 1 3 H An instruction operand may indicate an offset address in the data segment to be referenced. For example: DS:0016 ;INSTRUCTION OPERANDS We take the following as an example: WORDX DW 0 ; Define WORDX as word … MOV CX, WORDX ; Move data in memory ( the contents of WORDX ) to ; register ( CX ).--- Memory operand. MOV CX, 25 ; Move an immediate data ( 25 ) to register ( CX ). ; ----Immediate data operand. MOV CX, DX ; Move data between registers ( DX to CX ). ; ----Register operand. MOV CX, [ DI ] ; Move contents of location addressed by DS:DX. ; ----Index operand. NOTE:there is an error in text book here :MOV CX, [DX] ;the dx must be the DI or BX,or SI or BP register. KEY POINTS Ref. P28. QUESTIONS Ref. P28. ;Chapter 3 EXECUTING COMPUTER INSTRUCTIONS;DEBUG Commands DEBUG ‘s set of commands are all single or double character command. The most common commands are the follow: ( ? For help ) assemble A [address] dump D [range] enter E address [list] go G [=address] [addresses] name N [pathname] [arglist] proceed P [=address] [number] quit Q register R [register] trac