Connecting with Computer Science, 2e Chapter 9 Operating SystemsConnecting with Computer Science, 2e 2 Objectives • In this chapter you will: – Learn what an operating system is – Become familiar with different types of operating systems – Identify the major functions of an operating system – Understand how operating systems manage processesConnecting with Computer Science, 2e 3 Objectives (cont’d.) • In this chapter you will (cont’d.): – Understand how operating systems manage resources – Understand how operating systems provide security – Learn how to perform basic operating system file management functions in Windows and LinuxConnecting with Computer Science, 2e 4 Why You Need to Know About... Operating Systems • Operating system (OS) – Essential to the functioning of computers – Controls operations inside the computer • Operating system knowledge – Improves efficiencyWhat Is an Operating System? • Program responsible for managing the user interface, system resources, and processes • Software control center – Loaded when computer boots – Resident in main memory – Loads and supervises all other programs – Provides interface to CPU and I/O devices – Capable of connecting with standard devices • Written in programming languages: C and C++ Connecting with Computer Science, 2e 5Connecting with Computer Science, 2e 6 Figure 9-1, An OS provides an interface between the user, applications, and hardware What Is an Operating System? (cont’d.)Connecting with Computer Science, 2e 7 What Is an Operating System? (cont’d.) • Parts: – Kernel: core program loaded at boot time by BIOS • Small program • Remains in memory the entire time the computer is on – Modules: provide user and device interface • Main module responsible for user interface • Windows: provides graphical desktop • Linux: Gnome, KDE, or Xfce graphical interface • Drivers interface with I/O devices • Loaded onto computer’s hard disk or ROM chipConnecting with Computer Science, 2e 8 Figure 9-2, Users and computer components interact with the OS kernel What Is an Operating System? (cont’d.)Connecting with Computer Science, 2e 9 What Is an Operating System? (cont’d.) • Microsoft Windows – Most widely used OS • Disk Operating System (DOS) – Predecessor to Windows • Linux or UNIX is used on many servers • Macintosh is used in schools • OS running on a computer is called a platform – OS fitted to a particular CPU – Cross-platform application runs on multiple platformsConnecting with Computer Science, 2e 10 Table 9-1, OS development summary What Is an Operating System? (cont’d.)Connecting with Computer Science, 2e 11 Table 9-1, OS development summary (cont’d.) What Is an Operating System? (cont’d.)Connecting with Computer Science, 2e 12 Table 9-1, OS development summary (cont’d.) What Is an Operating System? (cont’d.)Types of Operating Systems • Classified by features or intended uses – Single-tasking: DOS and Windows 3.x • Allows running only one process (task) at a time – Multitasking: Windows, Linux, and Mac OS • Supports more than one process running at a time – Network operating systems (NOS): NetWare, UNIX, Linux, and Windows Server 2008 • Designed to provide strong network services – Multiprocessing • Coordinated execution of a process, using two or more CPUs at the same time Connecting with Computer Science, 2e 13Connecting with Computer Science, 2e 14 Types of Operating Systems (cont’d.) • Each OS is designed to be strong in a particular area – Microsoft Windows and Mac OS • Appeal to home and small-business users • Installed on the overwhelming majority of desktops – UNIX and Linux • Strong in multitasking, security, and multiprocessing • Known for stability • Server environment operating systems – Many other OSs run on PDAs and cell phonesConnecting with Computer Science, 2e 15 Functions of an Operating System • Basic functions – Provide a user interface – Schedule and manage program execution – Manage memory – Configure devices – Provide file management and security – Provide basic networking capability – Monitor performanceFunctions of an Operating System (cont’d.) • Four main categories – Providing a user interface – Managing processes – Managing resources (including memory) – Providing security Connecting with Computer Science, 2e 16Connecting with Computer Science, 2e 17 Providing a User Interface • User interface – Program enabling computer communication – DOS and Linux use a command-line interface • Sometimes called console operating systems • Command-line interface – Type commands and receive responses in text format • Command prompt – Words and symbols displayed onscreen that indicate the OS is waiting for user inputConnecting with Computer Science, 2e 18 Providing a User Interface (cont’d.) • Graphical user interface (GUI) – Information displayed in a graphical format • User can select items using a pointing device (e.g., mouse) – Clicking icons and buttons opens graphical windows and allows menu selectionsConnecting with Computer Science, 2e 19 Figure 9-3, The Windows command prompt emulates a DOS environment (top); the default GUI interface of Windows Vista (middle); and the GUI interface of Linux (bottom) Providing a User Interface (cont’d.)Connecting with Computer Science, 2e 20 Figure 9-3, (cont’d.) Providing a User Interface (cont’d.)Connecting with Computer Science, 2e 21 Providing a User Interface (cont’d.) • Windows command prompt access – Access at: All Programs, Accessories menu – Emulates a DOS environment – Provides backward compatibility • GUIs can be added to Linux – Standard Linux uses command-line interfaceManaging Processes • Operating system responsibilities – Loads, starts, supervises, and stops processes • Process – Each program running on a computer – May start (spawn) other processes to support them • Windows Task Manager shows running processes – Accessed by pressing Ctrl+Alt+Delete keys • Linux displays information on active processes
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