COMP 314 - U1C2

Operating System Concepts, Seventh Edition

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COMP 314 – Unit 2 (Notes) Operating System Services (USER) o User Interface (40) Three different types: GUI, CLI, Batch (system commands through a file). o Program Execution (40) The system must be able to load programs into memory and to run them. The program must be able to terminate programs either normally or abnormally (indicating errors). o I/O Operations (40) For efficiency and protection the user usually cannot control an I/O device directly, so the OS has to. o File-system manipulation (40) Programs need to read/write files and directories. They also need to create and delete them by name, search for a given file, and list file information. Some include the need for permission management to allow or deny access. o Communications (40) One process may need to communicate with another process, which is done through either shared memory, or message passing. Message passing is when packets of information are moved between processes by the OS. o Error Detection (40) Needs to be constantly aware of errors. May be CPU and memory hardware, I/O devices, user programs (arithmetic overflow, too-great use of CPU time, etc.) For each type of error, the OS should take appropriate action to ensure correct and consistent computing. Debugging facilities can greatly enhance the user’s and programmer’s abilities to use the system efficiently. Operating System Services (SYSTEM) o Resource Allocation (41) When there are multiple users or multiple jobs running at the same time, resources must be allocated to each one of them. Some (CPU cycles, main memory, and file storage) may have special allocation code, where others (such as I/O devices) may have a much more general request and release code. o Accounting (41) We want to keep track of which users use how much of which type of resources. Usage statistics may be a valuable tool for researches who wish to reconfigure the system to improve computing services. o Protection and Security (41) When several separate processes execute concurrently, it should not be possible for one process to interfere with the others or with OS itself. Protection involves ensuring that all access to system resources is controlled. Security of the system from outsiders is also important. User OS Interface o Command Interpreter (CLI) (41) Some OSs include a command interpreter in the kernel. Others, such as Win XP and Unix, treat the command interpreter as a special program that is running when a job is initiated or when a user first logs on. On systems where multiple interpreters are found they are known as shells (e.g. Bourne Shell, C Shell, etc.) Main function is to get and execute user-specified commands. There are two general ways in which commands can be implemented: (42)
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This note was uploaded on 07/18/2011 for the course COMP 314 taught by Professor Dr.dunwei(grant)wen during the Spring '11 term at Open Uni..

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COMP 314 - U1C2 - Athabasca university

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