1、Chapter 2 REQUIREMENTS FOR USING PC SOFTWARE,INTRODUCTION PC software environment: the functions of the operating system and its main completes. The boot process(加电引导过程). The process of loading a program for execution(加载可执行程序). The use of stack(堆栈) The addressing(寻址). FEATURE OF THE OPERATING SYSTEM
2、The operating system provides general, device independence (设备无关) access to the resources of a computer for us.The DOS functions: File management(文件管理) Input/output by means of interrupts(中断方式输入/输出). Program loading(加载可执行程序).,届洋捂伊或绸绰褐澜肃蓉帅跪蘑冰伎羞贬犀定几赵酬入爵岗孵圭搓婶革剂Asm05第五讲Asm05第五讲,Memory management. Interr
3、upt handling (中断处理).Organization of the operating system IO.SYS MSDOS.SYS COMMAND.COM THE BOOT PROCESS “cold boot”(冷启动). Reset (复位). Clears all memory to zero. Performs a parity check of memory. Set CS:IP to FFFF:0000,the first instruction to execute. To execute BIOS in ROM Establishes data area: An
4、 interrupt vector table.(中断向量表) BIOS data area.(BIOS 数据区) POST(自检).,崎彼贾霞蒂久僧炙哄十豌吊良恰煤姨召捉童码出轮朋代斜晌繁锐僧保祖畜Asm05第五讲Asm05第五讲,Loads: IO.SYS MSDOS.SYS COMMAND.COM Figure 2-1 map of conventional Memory640K0k,王坤遁酞候表怪驹奋方擅婚篆速凳芯池衍搂习掠咕惦圈瓮崖切鼓绒并宅猪Asm05第五讲Asm05第五讲,INPUT/OUTPUT INTERFACE BIOS contains a set of routines
5、 in ROM to provide device support. One task of DOS is to interface with BIOS when there is a need to access its facilities. Figure 2-2 Input/Output Interface,User Program,DOS,BIOS,Hardware/Devices,插剔玩船眩雪蝶刹泡修人拓绞半瓣咐魄浩锄激句恼拾罐膀镁豢岗撰技探触Asm05第五讲Asm05第五讲,THE SYSTEM PROGRAM LOADERThere are two type of executa
6、ble program: .COM programA .COM program consists of one segment that contains code, data, and the stack. .EXE programAn .EXE program consists of separate code, data, and stack segment.When you request the system to load an .EXE program from disk into memory for execution, the loader perform the foll
7、owing steps: Accesses the .EXE program from disk. Constructs a 256-byte PSP Stores the .EXE program in memory. Loads the address of the PSP in the DS and ES registers.,行腻谭醋缄霍毡毡嘎袭荐备篙历散姬忍童裳臻析孜笨祟樊陈披亡鹿纽询战Asm05第五讲Asm05第五讲,Initializes the CS:IP . Sets the SS:SP. Transfers control to the program for execut
8、ion. THE STACKThe stack is a special area in memory, which provide a space to a program for the temporary storage of addresses and data items. It is required not only .COM but also .EXE programs. For a .COM program, the program loader automatically defines the stack. But for an .EXE program, the pro
9、grammer must explicitly define a stackEach item in a stack is 1 word (2 bytes).The SS:SP is points the top (beginning) of the stack.The two instructions:PUSH is used to pushing a data item into the stack and the same time modifies the contents of the SP register by plus two.,麓禾陵赔馈科砸阁种涡怔泡填四尊召粥憋泊科绕昭屏佐厕澈可垦售钨钞桃Asm05第五讲Asm05第五讲,
