计算机科学概论重点

1. Real-time processing

⏹The interactive systems required that the activities taking place in a machine be

coordinated with the activities in the machine’s environment.

⏹This coordination called real-time processing.

⏹It could not support to serve more than one user.

Time-sharing processing

⏹The operating system rotated the various jobs in and out of execution by a

process called time-sharing.

⏹It is the technique of dividing time into intervals , or time slices, and restricting

the execution of a job to only one time slice at a time, one by one.

⏹Multitasking processing

⏹Time-sharing used in single user system called multitasking processing

⏹Advantage of time-sharing processing

⏹By rapidly shuffling the jobs in this manner, the illusion of several jobs executing

simultaneously is created.

⏹By it, the computer system does not spend much of its time waiting for peripheral

devices to complete tasks or for a user to make the next request.

⏹The two broad categories of machine’s software

⏹Application software

⏹System software

⏹Application software

⏹Consist of the programs for performing tasks particular to the machines’s

utilization.

⏹Examples of application software include spreadsheets, database systems,

desktop publishing systems, program development software, and games.

⏹System software

⏹It perform those tasks that are common to computer system in general. Providing

the environment for the application software.

⏹System software can divided into two categories: operating system and utility

software.

⏹Utility software

⏹Consist of program for performing activities that are fundamental to computer

installations yet not included in the operating system.

⏹It consist of software units that extend the capabilities of the operating system.

⏹Utility software examples: the software formatting a disk, copying a file,

communicating through a modem over telephone lines, compressing and

decompressing data, handing network communication.

⏹Shell

⏹The portion of operating system that define the interface between the operating

system and its user

⏹Kernel

⏹The internal part of an operating system, which contains those software

components that perform the very basic functions required by the computer

installation.

⏹Window manager and its functions

⏹ A major component within today’s GUI

⏹Allocating blocks of space on the screen –window, and keep track of which

application is associated with each window

⏹Placing the desired pattern in the window assigned to an application, and

monitoring mouse’s moving and acting.

⏹File manager

⏹Its job is to coordinate the use of machi ne’ mass storage facilities.

⏹Directory or folder: grouped file bundle

⏹User can organize their files according to their purposes by placing related files

in the same directory.

⏹Directory can set up in hierarchic structure, including directory and subdirectory

⏹Path: a chain of directories within directories is called directory path

⏹File descriptor:an area of main memory, where stored information needed to

find and manipulate the file

Virtual Memory: an illusionary memory area by rotating programs and data back and forth between main memory and mass storage.

Page: memory unit, typical page size is no more than four KB

⏹Scheduler

⏹It determines which activities are to be considered for execution in a time-sharing

system

⏹Dispatcher

⏹It controls the allocation of time slices to these activities

⏹Boot Strapping (or booting)

⏹ A procedure is performed by the machine each time it is turn on.

⏹ A CPU is designed so that its program counter starts with a particular

predetermined address each time the CPU is turn on

⏹At that address, the CPU expects to find the first instruction to be executed.

⏹The contents of that memory is permanent, the memory is read-only memory

(ROM)

⏹Bootstrap

⏹ A small program that is executed automatically when the machine is turned on

⏹What is a process