Xu Xuezhen group.ppt

1、presentation,1 Information=Bit+Context As we all know, each program is a sequence of bits,each with a value of 0 or 1,and 8-bit=1byte,each byte represents some text character in the program.But in most modern systems represent text character using the ASCII standard,for example,the/n corresponding t

2、o the integer value 10.,As for the Context,It was the only thing that distinguishes different data objects when we view them. 2 Programs are translated by other programs. If we want our programs can run on the system,the individual C statements must be translated by other programs into a sequence of

3、 low-level-machine-language instruction.So it s a necessary thing that we have to do.Just like the operating system have to through device drive to contral the hardware devices.,Compilation system 1.preprocessing phase pilation phase 3.assembly phase 4.linking phase,3 Understand how compilation syst

4、ems work can make a difference of our program. optimizing program performance understanding link-time error Avoiding security holes,How the “hello program” running in the hardware,Hardware Organization of a system,Made by 20121120178,BUSES,The buses can be divided into 3 types, the data bus, address

5、 bus and control bus. The data bus is used for transferring data. The address bus is used for transferring data address. The control bus is used for transferring the control signal.,Running through the system is a collection of electrical called buses.,I/O Devices,Input / output devices are the syst

6、ems connection to the external world. The example system has four I/O devices: a keyboard and mouse for user input, a display for user output, and a disk drive(硬盘驱动器) for long-term storage of data and programs.,Virtual Memory,By li jianqing,Whats virtual memory?,When your computer does not have enou

7、gh RAM to hold a program,it might use virtual memory.,There are a few pointsto note aboutthe virtual memory,1、Idea of extending memory 2、Is not the RAM 3、No fake but virtual,1、One way to extend the amount of memory accessible by a program is to use disk,2、,In effect,RAM acts like cache for disk.,3、T

8、he problem with disk is that its very slow to access.,Disk is easy to get many spaces for a small cost. But we still want to avoid accessing the disk unnecessarily.,Use of virtual memory,a、virtual memory is old concept b、People have virtual memory before they had cache c、virtual memory only appeared

9、 on mainframes for a long time,caches matter,What is cache? : Cache is a kind of special memory and is circuted on the processor chip.,Funcation,Now, maybe you are curious about the funcation of the cache? Or even you wonder whether the computer cant work without the cache. I must say that the computer can also work with out the cache. But it works too sl