Chapter 1: What is an Operating System? – A Practical Approach Introduction and Overview Romilla Chowdhuri Fall 2014 Chapter 1 What is an Operating System?2 Chapter 1 Objectives n Define Operating System (OS) n Explain OS interface n Abstraction n Black Box n Open Source and Proprietary3 What is an Operating System n The operating systems is a set of system software routines that sits between the application program and the hardware4 OS Interface n Points of connection or linkage q User interfaces with application program q Application program interfaces with operating system q Operating system interfaces with hardware n Application program accesses hardware q Through the operating systems q Following the operating system’s rules5 Operating System Services n Service q Software routine that runs in support of another program n Brief n Generally, a service performs single task n OS is a repository for common services q I/O support-open, close, read, write q Launch a program q And so on6 Operating Platforms n The operating system routines that interface with the application program represent a consistent platform for running application programs.7 Black Boxes n Abstraction q A simplified view of an object that ignores the internal details. n Layers of abstraction n Black Box q Inputs/outputs known q Contents hidden q Functionally independent8 Black Boxes (cont.) n To use a black box, all you must know are its interface rules. n Two black boxes communicate thorough a shared interface. n Viewing each layer of abstraction as black box allows to work with one layer at time.9 Modern Operating Systems n Modern operating systems are designed as a series of independent layers of abstraction linked by clearly defined interfaces. n An operating system can support many application programs© 2012 Pearson, Inc. Chapter 2 Networks and the Internet 10 Modern Operating Systems(cont.) n Apparent to user q Shell q File system q Device management n Transparent q Processor management q Memory management q Communication Services© 2012 Pearson, Inc. Chapter 2 Networks and the Internet 11 Handling a User Command n The user clicks Open n The shell interprets the command n File management finds a file n Device management read the file from disk12 Inter-computer Communication n Inter-computer communication is enabled by communication services installed on both machines.13 Operating System Philosophies n Open source q UNIX and Linux q Based on open, published source code n Proprietary q Apple Macintosh q Closed n Hybrid q Microsoft q Some elements open, some elements
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