APS审核—操作系统APS审核—操作系统.docVIP

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