Computer Science: Operating Systems PDF

Chapter 3: Operating Systems © 2015 Pearson Education Limited 2015  Chapter 3: Operating Systems Software Components System Sw vs. Application Sw Operating Systems © 2015 Pearson Education Limited 2015 3-2  Computer System  Hardware and Software Components The...

Chapter 3: Operating Systems © 2015 Pearson Education Limited 2015  Chapter 3: Operating Systems Software Components System Sw vs. Application Sw Operating Systems © 2015 Pearson Education Limited 2015 3-2  Computer System  Hardware and Software Components The software components are the collection of programs that execute in the computer. These programs perform computations, control, manage, and carry out other important tasks. Two general types of software components are: – System software – Application software © 2015 Pearson Education Limited 2015 3  Figure 3.3 Software classification © 2015 Pearson Education Limited 2015 3-4  Application Software © 2015 Pearson Education Limited 2015 5  System Software © 2015 Pearson Education Limited 2015 6  7 System Software 1. Utility Software  designed to help you monitor and configure settings for your computer system equipment, the operating system, or application software  Examples:  Security Software  Diagnostic Tools  Communication Programs © 2015 Pearson Education Limited 2015  8 System Software 2. Device Drivers  Software that helps a peripheral device establish communication with a computer  Used by printers, monitors, graphics cards…etc  Plug and play © 2015 Pearson Education Limited 2015  What is an Operating System? A large and complex software component for the operation and control of the computer system. It acts as an intermediary between a user and the computer system. Examples: Unix, MS Windows, MacOS, Linux, Sun Solaris, DEC VMS, etc. © 2015 Pearson Education Limited 2015 9  Modern Operating Systems Windows (Microsoft Corporation) these include a family of systems: 98, Me, CE, 2000, XP, Vista, Windows 7, and others Linux (Linus Torvalds, OSF GNU) MacOS (Apple) Solaris (Sun Microsystems) OSF-1 (OSF, DEC) IRIX (Silicon Graphics) OS2 (IBM) OS/390 (IBM) VMS (Dec/Compaq/HP) © 2015 Pearson Education Limited 2015 10  The Operating System A provider of services to user programs (via an interface) A huge resource manager © 2015 Pearson Education Limited 2015 11  Operating Systems Abstract Views External views – Set of interface of the computer system – A layer of software on top of the hardware Internal view – Resource manager - It controls and manages CPU, memory, I/O devices, etc. © 2015 Pearson Education Limited 2015 12  Operating System Components User Interface: Communicates with users – Text based (Shell) – Graphical user interface (GUI) Kernel: Performs basic required functions – File manager – Device drivers – Memory manager – Scheduler and dispatcher © 2015 Pearson Education Limited 2015 3-13  Figure 3.4 The user interface act as an intermediary between users and the operating system kernel © 2015 Pearson Education Limited 2015 3-14  Functional Components of an OS The most important components of an operating system are: Process manager Memory manager Resource manager File manager Device manager © 2015 Pearson Education Limited 2015 15  16 Operating System Managing Processor Resources  Multitasking Allows two or more tasks to run simultaneously  Multithreading Allows multiple parts (threads) within a single program to run simultaneously  Multiprocessing Supports a division of processes among multiple processors © 2015 Pearson Education Limited 2015 © 2015 Pearson Education Limited 2015 0-17  File Manager Directory (or Folder): A user-created bundle of files and other directories (subdirectories) Directory Path: A sequence of directories within directories © 2015 Pearson Education Limited 2015 3-18  19 Operating System Managing Storage Resources  File Directories and Folders © 2015 Pearson Education Limited 2015  Memory Manager Allocates space in main memory May create the illusion that the machine has more memory than it actually does (virtual memory) by playing a “shell game” in which blocks of data (pages) are shifted back and forth between main memory and mass storage © 2015 Pearson Education Limited 2015 3-20  Getting it Started (Bootstrapping) Boot loader: Program in ROM (example of firmware) – Run by the CPU when power is turned on – Transfers operating system from mass storage to main memory – Executes jump to operating system © 2015 Pearson Education Limited 2015 3-21  22 The Boot Process  Time between turning on a computer and loading OS  Steps:  Power up  Start boot program  Power-on self test  Identify peripheral devices  Load operating system  Check configuration and customization © 2015 Pearson Education Limited 2015  Figure 3.5 The booting process © 2015 Pearson Education Limited 2015 3-23  Security Attacks from outside – Problems Insecure passwords Sniffing software – Counter measures Auditing software © 2015 Pearson Education Limited 2015 3-24  Security (continued) Attacks from within – Problem: Uncontrollable processes – Counter measures: Control process activities via privileged modes and privileged instructions © 2015 Pearson Education Limited 2015 3-25  End of Chapter © 2015 Pearson Education Limited 2015