1. Chapter No 10System Software and Application Software

2. System Software Systemsoftware is computer software designed to operate and control the computer hardware and to provide a platform for running application software. The programs that are part of the system software include assemblers, compilers, file management tools, system utilities, and debuggers. 3. Operating System An operating system is a program designed to run other programson a computer. A computers operating system is its most important program. It is considered the backbone of a computer, managing bothsoftware and hardware resources. Operating systems are responsible for everything from the controland allocation of memory to recognizing input from external devices and transmitting output to computer displays. They also manage files on computer hard drives and controlperipherals, like printers and scanners. 4. Operating System Functions Many different operating systems exist, designedfor all types of computers. Regardless of the size of the computer, however, most operating systems provide similar functions. The operating system handles many of these functions automatically, without requiring any instructions from a user. Some functions of operating systems are discussed as under: 5. Operating System Functions Starting and Shutting Down a Computer The process of starting or restarting a computer is called booting. Turning on a computer is called cold boot. Warm boot is the process of using the operating system to restart acomputer. Each time you boot a computer, the kernel and frequentlyused operating system instructions are loaded, or copied, from storage into the computers memory (RAM). The kernel is the core of an operating system that manages memory and devices, maintains the computers clock, starts programs, and assigns the computers resources, such as devices, programs, data, and information. 6. Operating System Functions The steps in the following paragraphs explain what occurs during a cold boot on a personal computer using the Windows operating system. Step 1: When you turn on the computer, the power supply sends an electrical signal to the components in the system unit. Step 2: The charge of electricity causes the processor chip to reset itself and find the ROM chip(s) that contains the BIOS. The BIOS, which stands for basic input/output system, is firmware that contains the computers startup instructions. Step 3: The BIOS executes a series of tests to make sure the computer hardware is connected properly and operating correctly. The tests, collectively called the power-on self test (POST ), check the various system components including the buses, system clock, adapter cards, RAM chips, mouse, keyboard, and drives. As the POST executes, LEDs (tiny lights) flicker on devices such as the disk drives and keyboard. Beeps also may sound, and messages may appear on the screen. 7. Operating System Functions Step 4: The POST results are compared with data in a CMOS chip. CMOS is a technology that uses battery power to retain information when the computer is off. The CMOS Complementary metaloxide semiconductor chip stores configuration information about the computer, such as the amount of memory; type of disk drives, keyboard, and monitor; the current date and time; and other startup information. It also detects any new devices connected to the computer. If any problems are identified, the computer may beep, display error messages, or cease operating depending on the severity of the problem. 8. Operating System Functions Step 5: If the POST completes successfully, the BIOS searches for specific operating system files called system files. The BIOS may look first to see if a USB flash drive plugged in a USB port or a disc in an optical disc drive contains the system files, or it may look directly on drive C (the designation usually given to the first hard disk) for the system files. 9. Components of Computer Step 6: Once located, the system files load into memory (RAM) from storage (usually the hard disk) and execute. Next, the kernel of the operating system loads into memory. Then, the operating system in memory takes control of the computer. Step 7: The operating system loads system configuration information. In the latest Windows versions, the registry consists of several files that contain the system configuration information. 10. Boot Disk:A boot drive is the drive from which your personal computer boots (starts). In most cases, drive C (the hard disk) is the boot drive. Sometimes a hard disk becomes damaged and the computer cannot boot from the hard disk, or you may want to preview an operating system without installing it. In these cases, you can boot from a special disk, called a boot disk or a recovery disk, that contains a few system files that will start the computer.Providing a User Interface You interact with software through its user interface. That is, a user interface controls how you enter data and instructions and how information is displayed on the screen. Two types of user interfaces are graphical and command-line. Operating systems often use a combination of these interfaces to define how a user interacts with a computer. 11. Graphical User Interface Most users today work with a graphical user interface. With a graphical user interface (GUI), you interact with menus and visual images such as buttons and other graphical objects to issue commands. Many current GUI operating systems incorporate features similar to those of a Web browser, such as links and navigation buttons (i.e., Back button and Forward button). 12. Command-Line Interface To configure devices, manage system resources, and troubleshoot network connections, network administrators and other advanced users work with a command-line interface. In a command-line interface, a user types commands or presses special keys on the keyboard (such as function keys or key combinations) to enter data and instructions (Figure 8-5). Some people consider command-line interfaces difficult to use because they require exact spelling, grammar, and punctuation. Command-line interfaces, however, give a user more control to manage detailed settings. When working with a command-line interface, the set of commands entered into the computer is called the command language. 13. Managing Programs Some operating systems support a single user and only one running program at a time. Others support thousands of users running multiple programs.A single user/single tasking operating system allows only one user to run one program at a time. Early systems were single user/single tasking. Smart phones and other mobile devices, however, often use a single user/single tasking operating system. A single user/multitasking operating system allows a single user to work on two or more programs that reside in memory at the same time. When a computer is running multiple programs concurrently, one program is in the foreground and the others are in the background. The one in the foreground is the active program, that is, the one you currently are using. The other programs running but not in use are in the background. 14. Managing Memory The purpose of memory management is to optimize the use of random access memory (RAM). The operating system allocates, or assigns, data and instructions to an area of memory while they are being processed. Then, it carefully monitors the contents of memory. Finally, the operating system releases these items from being monitored in memory when the processor no longer requires them. If you have multiple programs running simultaneously, it is possible to run out of RAM, the operating system may have to use virtual memory to solve the problem. 15. Managing Memory With virtual memory, the operating system allocates a portion of a storage medium, usually the hard disk, to function as additional RAM. As you interact with a program, part of it may be in physical RAM, while the rest of the program is on the hard disk as virtual memory. Because virtual memory is slower than RAM, users may notice the computer slowing down while it uses virtual memory. The area of the hard disk used for virtual memory is called a swap file because it swaps (exchanges) data, information, and instructions between memory and storage. A page is the amount of data and program instructions that can swap at a given time. The technique of swapping items between memory and storage, called paging, is a time-consuming process for the computer. 16. Coordinating Tasks The operating system determines the order in which tasks are processed. A task, is an operation the processor manages. Tasks include receiving data from an input device, processing instructions, sending information to an output device, and transferring items from storage to memory and from memory to storage. A multiuser operating system does not always process tasks on a first-come, first-served basis. Sometimes, one user may have a higher priority than other users. In this case, the operating system adjusts the schedule of tasks. Sometimes, a device already may be busy processing one task when it receives a second task. This occurs because the processor operates at a much faster rate of speed than peripheral devices. 17. Configuring Devices A driver, short for device driver, is a small program that tells the operating system how to communicate with a specific device. Each device on a computer, such as the mouse, keyboard, monitor, printer, card reader/writer, and scanner, has its own specialized set of commands and thus requires its own specific driver. When you boot a computer, the operating system loads each devices driver. These devices will not function without their correct drivers. If you attach a new device to a computer, such as a printer or scanner, its driver must be installed before you can use the device. 18. Configuring Devices Today, most devices and operating systems support Plug and Play. Plug and Play means the operating system automatically configures new devices as you install them. Specifically, it assists you in the devices installation by loading the necessary drivers automatically and checking for conflicts with other devices. With Plug and Play, a user plugs in a device, turns on the computer, and then uses the device without having to configure the system manually. Devices that connect to a USB port on the system unit typically are Plug and Play. 19. Monitoring Performance Operating systems typically contain a performance monitor. A performance monitor is a program that assesses and reports information about various computer resources and devices. For example, users can monitor the processor, disks, network, and memory usage. The information in performance reports helps users and administrators identify a problem with resources so that they can try to resolve any problems. If a computer is running extremely slow, for example, the performance monitor may determine that the computers memory is being used to its maximum. Thus, you might consider installing additional memory in the computer. 20. Providing UtilitiesFileManagementandOtherOperating systems often provide users with the capability of managing files, searching for files, viewing images, securing a computer from unauthorized access, uninstalling programs, cleaning up disks, defragmenting disks, diagnosing problems, backing up files and disks, and setting up screen savers. 21. Updating Software Automatically Many popular programs, including most operating systems, include an automatic update feature that automatically provides updates to the program. With an operating system, these updates can include fixes to program bugs, or errors, enhancements to security, modifications to device drivers, access to new or expanded components such as desktop themes or games, and even updates to application software on the computer such as a Web browser. 22. Administering Security Computer and network administrators typically have an administrator account that enables them to access all files and programs on the computer or network, install programs, and specify settings that affect all users on a computer or network. Settings include creating user accounts and establishing permissions. These permissions define who can access certain resources and when they can access those resources. 23. Controlling a Network Some operating systems are designed to work with a server on a network. A server operating system is an operating system that organizes and coordinates how multiple users access and share resources on a network. Resources include hardware, software, data, and information. For example, a server operating system allows multiple users to share a printer, Internet access, files, and programs. Some operating systems have network features built into them. In other cases, the server operating system is a set of programs separate from the operating system on the client computers that access the network. 24. Types of Operating Systems: The three basic categories of operating systems that exist today are stand-alone, server, and embedded. Astand-alone operating system is a complete operatingsystem that works on a desktop computer, notebook computer, or mobile computing device. Some stand-alone operating systems are called client operating systems because they also work in conjunction with a server operating system. Client operating systems can operate with or without a network. Other stand-alone operating systems include networking capabilities, allowing the home and small business user to set up a small network. Examples of currently used stand-alone operating systems are Windows Vista, Mac OSX, UNIX, and Linux. 25. Server Operating Systems A server operating system is an operating system that is designed specifically to support a network. A server operating system typically resides on a server. The client computers on the network rely on the server(s) for resources. To meet the needs of all sizes of businesses, the Windows Server 2008 family includes many editions, with the more common listed below: Windows Server 2008 Standard for the typical small- to medium-sized business network Windows Server 2008 Enterprise for medium to large-sized businesses, including those with e-commerce operations Windows Server 2008 Datacenter for businesses with huge volumes of transactions and large-scale databases. 26. Embedded Operating Systems The operating system on mobile devices and many consumer electronics, called an embedded operating system, resides on a ROM chip. Popular embedded operating systems today include Windows Mobile, Palm OS, iPhone OS, BlackBerry, embedded Linux, and Symbian OS. 27. Application Software Application software is all the computer software that causes a computer to perform useful tasks beyond the running of the computer itself. Also known as software application, application program or application. The term is used to contrast such software with system software, which manages and integrates a computer's capabilities but does not directly perform tasks that benefit the user. The system software serves the application, which in turn serves the user. 28. In information technology, an application is a computer program designed to help people perform an activity. An application thus differs from an operating system (which runs a computer), a utility (which performs maintenance or generalpurpose chores), and a programming tools (with which computer programs are created). Examples include accounting software, enterprise software, graphics software, media players, and office suites. Many application programs deal principally with documents. Applications may be bundled with the computer and its system software or published separately. 29. Application software classification There are many types of application software: An application suite consists of multiple applications bundled together. They usually have related functions, features and user interfaces, and may be able to interact with each other, e.g. open each other's files. Business applications often come in suites, e.g. Microsoft Office, and iWork, which bundle together a word processor, a spreadsheet, etc.; but suites exist for other purposes, e.g. graphics or music. Enterprise software addresses the needs of an entire organization's processes and data flow, across most all departments, often in a large distributed environment. (Examples include financial systems, customer relationship management (CRM) systems and supply chain management software). 30. Enterprise infrastructure software provides common capabilities needed to support enterprise software systems. (Examples include databases, email servers, and systems for managing networks and security.)Information worker software lets users create and manage information, often for individual projects within a department, in contrast to enterprise management. Examples include time management,resourcemanagement,documentationtools,analytical, and collaborative. Word processors, spreadsheets, email and blog clients, personal information system, and individual media editors may aid in multiple information worker tasks. 31. Simulation softwaresimulates physical or abstract systemsfor either research, training or entertainment purposes.Media development softwaregeneratesprintandelectronic media for others to consume, most often in a commercial or educational setting. This includes graphic-art software, desktop publishing software, multimedia development software, HTML editors,digital-animationeditors,composition, and many others.digitalaudioandvideo 32. Product engineering software is used in developing hardware and software products. This includes computer-aided design (CAD), computer-aided engineering (CAE), computer language editing and compiling tools, integrated development environments, and application programmer interfaces.