OSCh2 - Chapter 2: OS Structures OS Structures 1 Objectives...

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OS Structures 1 OS Structures 1 Chapter 2: OS Structures 2 Objectives ! To describe the services an operating system provides to users, processes of the system. ! To discuss the various ways of structuring an operating system. ! To explain how operating systems are installed and customized and how they boot.
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OS Structures 2 3 Operating System Services ! One set of operating-system services provides functions that are helpful to the user (or user processes) : " User interface - almost all operating systems have a user interface (UI). # Command-line interface (CLI): require a program to allow entering and editing of text commends. # Graphics user interface (GUI): a window system with a pointing device and a keyboard to enter commends. # Batch : commands and directives are entered into files to be executed. " Program execution - the system must be able to load a program into memory and to run that program, end execution, either normally or abnormally. 4 Operating System Services (cont’d) " I/O operations - a user program may require I/O. # For efficiency and protection, users cannot control I/O devices directly. # The operating system must provide a means to do I/O. " File-system manipulation - user programs need to read/write/create/delete/search files and directories. # The operating system provides permission management to allow or deny access to files or directories. " Communications user processes may exchange information, on the same computer or between computers over a network. # Communications may be via shared memory or through message passing . " Error detection the operating system needs to be constantly aware of possible errors. # And fix errors generated from hardware (disk fail) or software (arithmetic error).
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OS Structures 3 5 Operating System Services (cont’d) ! For systems with multiple users (processes) , another set of operating-system functions exists for ensuring the efficient operation of the system itself . " Resource allocation - when multiple users or multiple jobs running concurrently, resources must be allocated to each of them. # CPU, memory, file storage # Operating systems have CPU-scheduling routines to determine the best way to use the CPU. " Accounting - To keep track of which users use how much and what kinds of computer resources. # Usage statistics may be a valuable tool for researchers who wish to reconfigure the system to improve computing services. 6 Operating System Services (cont’d) " Protection and security - a multiuser or networked computer system may want to control use of user information. # Concurrent processes should not interfere with each other. # Protection involves ensuring that all access to system resources is controlled. # Security of the system from outsiders requires user authentication, extends to defending external I/O devices (e.g., network adapters) from invalid access attempts.
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OS Structures 4 7 CLI !
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This note was uploaded on 03/01/2012 for the course CMP 426 taught by Professor Gwangs.jung during the Spring '12 term at CUNY Lehman.

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OSCh2 - Chapter 2: OS Structures OS Structures 1 Objectives...

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