APS审核—操作系统APS审核—操作系统.doc
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操作系统
Operating System
What is an Operating System?
A program that acts as an intermediary between a user of a computer and the computer hardware
Operating system goals:
Execute user programs and make solving user problems easier
Make the computer system convenient to use
Use the computer hardware in an efficient manner
Computer System Structure
Computer system can be divided into four components
Hardware – provides basic computing resources
CPU, memory, I/O devices
Operating system
Controls and coordinates use of hardware among various applications and users
Application programs – define the ways in which the system resources are used to solve the computing problems of the users
Word processors, compilers, web browsers, database systems, video games
Users
People, machines, other computers
Operating System Definition
OS is a resource allocator
Manages all resources
Decides between conflicting requests for efficient and fair resource use
OS is a control program
Controls execution of programs to prevent errors and improper use of the computer
No universally accepted definition
?The one program running at all times on the computer” is the kernel.
Everything else is either a system program (ships with the operating system) or an application program
Computer System Organization
Computer-System Architecture
Most systems use a single general-purpose processor (PDAs through mainframes)
Most systems have special-purpose processors as well
Multiprocessors systems growing in use and importance
Also known as parallel systems, tightly-coupled systems
Advantages include
1.Increased throughput
2.Economy of scale
3.Increased reliability – graceful degradation or fault tolerance
Two types
1.Asymmetric Multiprocessing
2.Symmetric Multiprocessing
Operating-System Operations
Interrupt driven by hardware
Software error or request creates exception or trap
Division by zero, request for operating system service
Other process problems include infinite loop, process
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