1、UNIT8 Operating System 8-1 Technical Part8-2 Reading Material 8-1 Technical Part 8-1-1 DefinitionAn operating system is a program designed to run other programs on a computer.A computers operating system is its most important program.It is considered the backbone of a computer,managing both software
2、 and hardware resources.Operating systems are responsible for everything from the control and allocation of memory to recognizing input from external devices and transmitting output to computer displays.They also manage files on computer hard drives and control peripherals,like printers and scanners
3、.8-1-2 IntroductionsFunctionalities of Operating SystemThe operating system of a large computer system has even more work to do.Such operating systems monitor different programs and users,making sure everything runs smoothly,without interference,despite the fact that numerous devices and programs ar
4、e used simultaneously.An operating system also has a vital role to play in security.Its job includes preventing unauthorized users from accessing the computer system.Today most operating systems perform the following important functions:1.Process ManagementA process is a program in execution.A proce
5、ss needs certain resources,including CPU time,memory,files,and I/O devices,to accomplish its task.OS responsibilities for process management include:process creation and deletion;process scheduling,suspension,and resumption;process synchronization,inter-process communication.2.Memory ManagementMemor
6、y is a large array of addressable words or bytes or a data repository shared by the CPU and I/O devices.OS responsibility for memory management include:Allocate and deallocate memory space as requested;Keep track of which parts of memory are currently being used and by whom;Efficient utilization whe
7、n the memory resource is heavily competed.3.File ManagementThe operating system also handles the organisation and tracking of files and directories(folders)saved or retrieved from a computer disk.The file management system allows the user to perform such tasks as creating files and directories,renam
8、ing files,coping and moving files,and deleting files.The operating system keeps track of where files are located on the hard drive through the type of file system.The two main types of file system are File Allocation table(FAT)or New Technology File system(NTFS)4.Hardware ManagementOperating systems
9、 interface with hardware drivers that manage the actual physical hardware such as hard drives,modems,processors,memory and printers.The hardware drivers provide a layer of abstraction so that the operating system does not have to know about a specific device,but rather how to communicate with its dr
10、iver.The driver typically has to play by certain rules that the operating system expects,allowing driver software updates without disruption.5.User Interface ManagementThe operating system also manages the user interface,whether graphical or text-based.This function does involve the hardware managem
11、ent component mentioned above,but on a more advanced level.The user interface must respond to the users directions via mouse,keyboard,touch screen or other input device.The part of the operating system that manages this function must translate key presses,mouse clicks and other user actions into the
12、 appropriate commands to the other parts of the computer.6.Priority ManagementThe operating system must prioritize and manage the scheduling of the various applications running on the computer.For instance,if you are downloading a large file,but want to work on a document while it downloads,the oper
13、ating system slices the processor availability to give priority to your input actions while managing the download in the background.This is sometimes called preemptive scheduling,as anything that the user does takes priority and preempts other less important tasks.This ability to carve up processor
14、time gives what is actually a single-tasking OS the appearance of a multi-tasking OS.7.Task ManagementThe operating system performs basic computer tasks,such as managing the various peripheral devices such as the mouse,keyboard and printers.For example,most operating systems now are plug and play wh
15、ich means a device such as a printer will automatically be detected and configured without any user intervention.Classification of Operating SystemOperating systems can be classified as follows:1.Multi userMulti user operating systems allow two or more users to run programs at the same time.Some ope
16、rating systems permit hundreds or even thousands of concurrent users.The operating systems of mainframes and minicomputers are multi user system.2.MultiprocessingMultiprocessing refers to a computer system ability to support more than one process at the same time.Multiprocessing operating systems en
17、able several programs to run concurrently.MVS and UNIX are two of the most widely used multiprocessing systems,but there are many others,including OS/2 for high end PCs.3.MultitaskingMultitasking allows more than one program to run concurrently.Multitasking is the ability to execute more than one ta
18、sk at the same time,a task being a program.The terms multitasking and multiprocessing are often used interchangeably,although multiprocessing sometimes implies that more than one CPU is involved.4.MultithreadingMultithreading allows different parts of a single program to run concurrently.Multithread
19、ing is the ability of an operating system to execute different parts of a program called threads,simultaneously.5.Real timeReal time operating system is systems that respond to input immediately.This category includes operating systems designed substantially for the purpose of controlling and monito
20、ring external activities with timing constraints.They are used for such tasks as navigation,in which the computer must react to a steady flow of new information without interruption.Several Commonly Used Operating SystemOperating systems provide a software platform on top of which other programs,cal
21、led application programs,can run.It is shown in Figure 8-1.The application programs must be written to run on top of a particular operating system.Your choice of operating system,therefore,determines to a great extent the applications you can run.For PCs,the most popular operating systems are DOS,OS
22、/2,and Windows,but others are available,such as Linux.Figure 8-1 Position of operating system1.WindowsWindows,in computer science,is a personal computer operating system sold by Microsoft Corporation that allows users to enter commands with a point-and-click device,such as a mouse,instead of a keybo
23、ard.The Windows operating system provides users with a Graphical User Interface(GUI),which allows them to manipulate small pictures,called icons,on the computer screen to issue commands.Windows is the most widely used operating system in the world.It is an extension of and replacement for Microsofts
24、 Disk Operating System(MS-DOS).The Windows GUI is designed to be a natural,or intuitive,work environment for the user.With Windows,the user can move a cursor around on the computer screen with a mouse.By pointing the cursor at icons and clicking buttons on the mouse,the user can issue commands to th
25、e computer to perform an action,such as starting a program,accessing a data file,or copying a data file.Other commands can be reached through pull-down or click-on menu items.The computer displays the active area in which the user is working as a window on the computer screen.The currently active wi
26、ndow may overlap with other previously active windows that remain open on the screen.This type of GUI is said to include WIMP features:windows,icons,menus,and pointing device(such as a mouse).2.UNIXUNIX,in computer science,is a multiuser,multitasking operating system originally developed by Ken Thom
27、pson and Dennis Ritchie at AT&T Bell Laboratories in 1969 for use on minicomputers(See Figure 8-2).UNIX exists in various forms and implementations;among these are versions developed at the University of California at Berkeley(known as BSD releases)and versions released by AT&T,the most recent being
28、 AT&T System V.UNIX is considered a powerful operating system which,because it is written in the C language,is more portableless machine-specificthan other operating systems.UNIX is available in several related forms,including AIX,a version of UNIX adapted by IBM(to run on RISC-based workstations),A
29、/UX(a graphical version for the Apple Macintosh),and Mach(a rewritten but essentially UNIX-compatible operating system for the NeXT computer).Its popularity is due in large part to the growth of the interconnected computer network known as the Internet,the software for which initially was designed f
30、or computers that ran UNIX.Variations of UNIX include SunOS(distributed by SUN Microsystems Inc.),Xenix(distributed by Microsoft Corporation),and Linux.UNIX and its clones support multitasking and multiple users.Its file system provides a simple means of organizing disk files and lets users protect
31、their files from other users.The commands in UNIX are not intuitive,however,and mastering the system is difficult.Figure 8-2 Unix System Interface 3.LinuxLinux(/5links/)is a UNIX-like computer operating system assembled under the model of free and open source software development and distribution(Se
32、e Figure 8-3).The defining component of Linux is the Linux kernel,an operating system kernel first released 5 October 1991 by Linus Torvalds.Linux was originally developed as a free operating system for Intel x86-based personal computers.It has since been ported to more computer hardware platforms t
33、han any other operating system.It is a leading operating system on servers and other big iron systems such as mainframe computers and supercomputers:more than 90%of todays 500 fastest supercomputers run some variant of Linux,including the 10 fastest.Linux also runs on embedded systems(devices where
34、the operating system is typically built into the firmware and highly tailored to the system)such as mobile phones,tablet computers,network routers,televisions and video game consoles;the Android system in wide use on mobile devices is built on the Linux kernel.Figure 8-3 Graphical login interface of
35、 Red Flag LinuxThe development of Linux is one of the most prominent examples of free and open source software collaboration:the underlying source code may be used,modified,and distributedcommercially or non-commerciallyby anyone under licenses such as the GNU General Public License.Typically Linux
36、is packaged in a format known as a Linux distribution for desktop and server use.Some popular mainstream Linux distributions include Debian(and its derivatives such as Ubuntu),Fedora and openSUSE.Linux distributions include the Linux kernel,supporting utilities and libraries and usually a large amou
37、nt of application software to fulfill the distributions intended use.4.VxWorksVxWorks is a real-time operating system(RTOS)that can be used in embedded systems(See Figure 8-4).VxWorks can be customized easily and can run on most processors designed for distributed computing.VxWorks is used to contro
38、l network and communication devices,test and measurement equipment,computer peripherals,automotive systems,avionics(aeronautics and astronautics)equipment and diverse consumer products.VxWorks has some similarities to UNIX and includes a shell,debugging functions,memory management,performance monito
39、ring and support for multiprocessing.The OS includes a kernel for preemptive multitasking,interrupt response,interprocess communication and a file system.Programming in VxWorks can be difficult for novices because the programmer must write the code on an as-needed basis.However,the fact that there i
40、s minimal content to save and restore means that VxWorks uses less processing power than UNIX,so it can run faster.VxWorks is a trademark of Wind River Systems,a company specializing in software optimization and based in Alameda,California,USA.Figure 8-4 Development tool interface of VxWorks8-1-3 Ap
41、plication Case or Example Windows 7 Operating SystemWindows 7 is the current release of Microsoft Windows,a series of operating systems produced by Microsoft for use on personal computers,including home and business desktops,laptops,netbooks,tablet PCs,and media center PCs.Windows 7 was released to
42、manufacturing on July 22,2009,and reached general retail availability worldwide on October 22,2009,less than three years after the release of its predecessor,Windows Vista.Windows 7s server counterpart,Windows Server 2008 R2,was released at the same time.Unlike Windows Vista,which introduced a large
43、 number of new features,Windows 7 was intended to be a more focused,incremental upgrade to the Windows line,with the goal of being compatible with applications and hardware with which Windows Vista was already compatible.Presentations given by Microsoft in 2008 focused on multi-touch support,a redes
44、igned Windows shell with a new taskbar,referred to as the Superbar,a home networking system called HomeGroup,and performance improvements.Some standard applications that have been included with prior releases of Microsoft Windows,including Windows Calendar,Windows Mail,Windows Movie Maker,and Window
45、s Photo Gallery,are not included in Windows 7;most are instead offered separately at no charge as part of the Windows Live Essentials suite.Only several functions of Windows 7 are shown below.1.Windows 7 Taskbar You can do so much more from the Windows 7 taskbar(See Figure 8-5).Windows 7s taskbar is
46、 greatly improved in two ways.First,you can pin programs to it indefinitely for easy quick launch.Second,on a crowded desktop covered with windows,using the new Aero Peek feature,you can preview individual windows from grouped taskbar applications,and even close documents from the thumbnails themsel
47、ves.Hold your mouse over the thumbnail to see an even larger view of the file.You can also rearrange and organize buttons on the taskbar,including pinned programs and running programs that arent pinned,so they appear in the order you prefer.To rearrange the order of buttons on the taskbar,drag a but
48、ton from its current position to a different position on the taskbar&as often as you like.Figure 8-5 Windows 7 Taskbar2.Show Desktop Show desktop on far right corner,but you dont need to click,just put your mouse over it.If you want to keep the desktop&minimize the files,just click it(See Figure 8-6
49、).Figure 8-6 Windows 7 Show Desktop3.Start Menu In Windows 7,you have much more control over the programs and files that appear on the Start menu(See Figure 8-7).The Start menu is essentially a blank slate that you can organize and customize to suit your preferences.Find a program you want to add&ri
50、ght mouse click&choose add to start menu.Click on the Start button on left bottom corner.Figure 8-7 Windows 7 Start MenuThe Start Menu List(See Figure 8-8)will appear&if you hold your mouse over the program you will see a list of recently opened files used by that program on the right.This also show
