A) Define operating systems and describe its many functions.
What is operating systems?
An operating system is a types of system software that is a set of programs containing instructions that work together to coordinate all the activities among computer hardware resources. Most operating systems perform similar functions that include starting and shutting down a computer, providing a user interface, managing programs, managing memory, coordinating tasks, configuring devices, establishing an Internet connection, monitoring performance, providing file management and other utilities, and automatically updating itself and certain utility programs. Some operating system also allow users to control a network and administer security.
Although an operating system can run from an optical disc and flash memory mobile media, in most cases, the operating system is installed and resides on the computer's hard disk. On handheld computers and many mobile devices such as smart phones, the operating system may reside on a ROM chip.
Different sizes of computers typically use different operating systems because operating system generally are written to run on a specific type of computer. For example, a mainframe computer does not use the same operating system as a personal computer. Even the same types of computers, such as desktop computers, may not use the same operating system. Some, however, can run multiple operating systems. When purchasing application software, you must ensure that it works with the operating system installed on your computer or mobile device.
The operating system that a computer uses sometimes is called the platform. With purchased application software, the package or specifications identify the required platform. A cross-platform program is one that runs the same on multiple operating systems.
Type of operating system functions
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Many different operating systems exist, designed for all types of computers. Regardless of the size of the computer, however, most operating systems provide similar functions. The following sections discuss functions common to most operating systems. The operating system handles many of these functions automatically, without requiring any instructions from a user.
So now lets me describe 12 types of operating system functions.
1) Starting and Shutting Down a computer
The process of starting or restarting a computer is called booting. When turning on a computer that has been powered off completely, you are performing a cold boot. A warm boot, by contrast, is the process of using the operating system to restart a computer. A warm boot properly closes any running processes and programs. However, it does not save any unsaved work. Thus, always remember to save your work before rebooting (restarting) a computer. With Windows, you can perform a warm boot by clicking the Start button arrow on the Start menu, and then clicking Restart on the Lock button menu.
When you install new software or update existing software, often an on-screen prompt instructs you to restart the computer. In this case, a warm boot is appropriate. If the computer stops responding, try pressing the power button to turn off the computer. As a last resort, remove power from the computer and then restart the computer. On newer computers, pressing the power button momentarily is the same as a warm boot, whereas pressing and holding the power button does not properly close running processes and programs.
The kernal is the core of an operating system that manages memory and devices, maintains the computer's clock, starts programs, and assigns the computer's resources, such as devices, programs, data, and information. The kernel is memory resident,which means it remains in memory while the computer is running.
A boot drive is the drive from which your personal computer boots (starts). In most cases, drive C ( 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. When the word, Live, is used with a type of media, such as Live CD or Live USB, this usually means the media can be used to boot the computer.
Shut Down options
Although some users leave their computers running continually and never turn them off, others choose to shut them down. Shut down options including powering off the computer, placing the computer in sleep mode, and hibernating the computer. Both sleep mode and hybernate, which store the current state of all open programs and documents, are designed to save time when you resume working on the computer. Sleep mode saves any open documents and programs to RAM, turns off all unneeded functions, and then places the computer in a low-power state. If, for some reason, power is removed from a computer that is in sleep mode, any unsaved work cold be lost. Hybernate, by contrast, saves any open documents and programs to a hard disk before removing power from the computer.
2) Provide 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 interface are graphical and command-line. Operating systems often use a combination of these interfaces to define how a user interacts with a computer.
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.
Windows, for example, offers two different GUIs, depending on your hardware configuration. Computers with less than 1 GB of RAM work with the Windows Vista Basic interface. Computers with more than 1 GB of RAM that have the required hardware may be able to work with the Windows Vista Aero interface.
To configure devices, manage system resources, and trouble-shoot 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 key or key combinations ) to enter data and instructions.
Some people consider command-line interfaces difficult to use because they require exact spelling, grammar, and punctuation. Minor errors, such as a missing period, generate an error message. 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.
3) 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. How an operating system handles programs directly affects your productivity.
A single user/single tasking operating system allows only one user to run one program at a time. For example, if you are working in a graphic program and want to check email messages, you must quit the graphics program before you can run the email program. Early systems were single user/single tasking . Smart phones and other mobile devices, however, often use a single user/single tasking operating system. Most other operating systems today are multitasking.
A multitasking operating system allows a single user to work on two or more programs that reside in memory at the same time. Using the example just cited, if you are working with a multitasking operating system, you do not have to quit the graphics program to run the email program. Both programs can run concurrently. Users today typically run multiple programs concurrently. It is common to have an email program and Web browser open at all times, while working with application programs such as word processing or graphics.
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.The foreground program typically displays on the desktop, and the background programs are hidden partially or completely behind the foreground program. You easily can switch between foreground and background programs. To make a program active in Windows, click its program button on the task bar. This causes the operating system to place other programs in the background.
The foreground program typically displays on the desktop, and the background programs are hidden partially or completely behind the foreground program. You easily can switch between foreground and background programs. To make a program active in Windows, click its program button on the taskbar. This causes the operating system to place all other programs in the background.
In addition to application programs, an operating system manages other processes. These processes include utilities or routines that provide support to other programs or hardware. Some are memory resident. Others run as they are required.
Some operating systems use preemptive multitasking to prevent any one process from monopolizing the computer's resources. With preemptive multitasking, the operating system interrupts a program that is executing and passes control to another program waiting to be executed. An advantage of preemptive multitasking is the operating system regains control if one program stops operating properly.
A multiuser operating system enables two or more users to run programs simultaneously. Networks, servers, mainframes, and supercomputers allow hundreds to thousands of users to connect at the same time, and thus are multiuser.
A multiprocessing is an operating system supports two or more processors running programs at the same time. Multiprocessing involves the coordinated processing of programs by more than one processor. Multiprocessing increases a computer's processing speed.
4) Managing Memory
The purpose of memory management is to optimize the use of random access memory (RAM). As Chapter 4 discussed, RAM consists of one or more chips on the motherboard that hold items such as data and instructions while the processor interprets and executes them. 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.
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 its swap 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, calling paging, is a time-consuming process for the computer.
When an operating system spends much of its time paging, instead of executing application software, it is said to be thrashing. If application software, such as a Web browser, has stopped responding and the hard disk's LED blinks repeatedly, the operating system probably is thrashing.
Instead of using a hard disk as virtual memory, Windows users can increase the size of memory through Windows ReadyBoost, which can allocate up to 4 GB of removable flash memory devices as additional memory cache. Users notice better performance with Windows ReadyBoost versus hard disk virtual memory because the operating system accesses a flash memory device, such as USB flash drive or SD memory card, more quickly than it acceses a hard disk.
5) Coordinating Tasks
The operating system determines the order in which tasks are processed. A task, or job, is an operation the processor manages. Tasks include receiving data from an input device, processing instructions, sending information to an output device, and transfering 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. For example, if the processor sends five documents to a printer, the printer can print only one document at a time and store as many documents as its memory can handle.
While waiting for devices to become idle, the operating system places items in buffers. A buffer is a segment of memory or storage in which items are placed while waiting to be transferred from an input device or to an output device.
The operating system commonly uses buffers with printed documents. This process, called spooling, sends documents to be printed to a buffer instead of sending them immediately to the printer. If a printer does not have its own internal memory or if its memory is full, the operating system's buffer holds the documents waiting to print while the printer prints from the buffer at its own rare of speed. By spooling documents to a buffer, the processor can continue interpreting and executing instructions while the printer prints. This allows users to work on the computer for other activities while a printer is printing. Multiple documents line up in a queue (pronounced Q) in the buffer. A program, called a print spooler, intercepts documents to be printed from the operating system and places them in the queue.
6) 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, 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 device's driver. These device 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. 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 device's 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.
Manufacturers often update a device's driver. For example, the update may enable the device to work with a new operating system, or it may improve the reliability of the device. You can visit the manufacturer's Web site to determine if a driver has been updated. In some cases, you may be notified that a driver has been updated. Always be sure to install updated drivers.
7) Establishing an Internet Connection
Operating systems typically provide a means to establish Internet connections. For example, Windows automatically configures some broadband Internet connections as soon as you connect to the broadband line. Otherwise, Windows includes a ' Connect to a network' wizard that guides users through the process of setting up a connection between a computer and an Internet access provider.
Some operating systems also include a Web browser and an email program, enabling you to begin using the Web and communicate with others as soon as you set up the Internet connection. Some also include utilities to protect computers from unauthorized intrusions and unwanted software such as viruses and spyware.
8) 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 computer's memory is being used to its maximum. Thus, you might consider installing additional memory in the computer.
9) Providing File Management and Other Utilities
Operating 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.
10) 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 or an email program.
Many software makers provide free downloadable updates, sometimes called a service pack, to users who have registered and activated their software. With operating systems, the automatic update feature automatically alerts users when an update is available. Further, it can be configured to download and install the update automatically.
11) 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 computer that access the network. When not connected to the network, the client computers use their own operating system. When connected to the network, the server operating system may assume some of the operating system functions.
The network administrator, the person over seeing network operations, uses the server operating system to add and remove users, computers, and other devices to and from the network. The network administrator also uses the server operating system to install software and administer network security.
12) 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. Setting include creating user accounts and establishing permissions. These permissions define who can access those resources and when they can access those resources.
For each user, the computer or network administrator establishes a user account, which enables a user to access, or log on to a computer or a network. Each user account typically consists of a user name and password. A user name, or user ID, is a unique combination of characters, such as letters of the alphabet or numbers, that identifies one specific user. Many users select a combination of their first and last names as their user name. A user named Henry Baker might choose H Baker as his user name.
A password is a private combination of characters associated with the user name that allows access to certain computer resources. Some operating systems allow the computer or network administrator to assign passwords to files and commands, restricting access to only authorized users.
To prevent unauthorized users from accessing computer resources, keep your password confidential. While users type as password, most computers hide the actual password characters by displaying some other characters, such as asterisks or dots. After entering a user name and password, the operating system compares the user's entry with a list of authorized user names and password. If the entry matches the user name and password kept on file, the operating system grants the user access. If the entry does not match, the operating system denies access to the user.
The operating system records successful and unsuccessful logon attempts in a file. This allows the computer or network administrator to review who is using or attempting to use the computer. The administrators also use these files to monitor computer usage.
To protect sensitive data and information further as it travels over a network, the operating system may encrypt it. Encryption is the process of encoding data and information into an unreadable form. Administrators can specify that data be encrypted as it travels over a network to prevent unauthorized users from reading the data. When an authorized user attempts to read the data, it automatically is decrypted, or converted back into a readable form.
Gary B, Shelly,Misty E. Vermaat (2010). Discovering Computers 2010: Living in a Digital World, Complete, Cengage Learning. ISBN-13: 9780324786453 (textbook)