The mall objective of real-time operating systems is their quick and predictable espouse to events. They have an event-driven or time-sharing design and often aspects of both. An event-driven system switches between tasks based on their priorities or external events while time-sharing operating systems switch tasks based on clock Interrupts. 2. Multi-user A multi-user operating system allows multiple users to access a computer system concurrently.
Time-sharing system can be classified as multi-user systems as they enable a multiple user access to a computer through the sharing of time. Single-user operating systems, as opposed to a multi-user operating system, are usable by a single user at a time. Being able to use multiple accounts on a Windows operating system does not make it a multi-user system. Rather, only the network administrator is the real user. But for a UNIX-Kick operating system, it is possible for two users to login at a time and this capability of the SO makes it a multi-user operating system. . Multi-tasking vs.. Single-tasking when only a single program Is allowed to run at a time, the system Is grouped under a single-tasking system. However, when the operating system allows the execution of multiple tasks at one time, it is classified as a multi-tasking operating system. Multi- asking can be of two types: pre-emotive or co-operative. In pre-emotive multitasking, the operating system slices the CPU time and dedicates one slot to each of the programs.
Unix-like operating systems such as Solaris and Linux support pre-emotive multitasking, as does Amigos. Cooperative multitasking is achieved by relying on each process to give time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking. 32-blat versions, both Windows NT and Win, used pre-emotive multi-tasking. Mac SO prior to SO X used to support cooperative multitasking. 4. Distributed A distributed operating system manages a group of independent computers and makes them appear to be a single computer.
The development of networked computers that could be linked and communicate with each other gave rise to distributed computing. Distributed computations are carried out on more than one machine. When computers in a group work in cooperation, they make a distributed system. 5. Embedded Embedded operating systems are designed to be used In embedded computer systems. They are designed to operate on small machines like Pads with less very compact and extremely efficient by design.
Windows CE and Minx 3 are some examples of embedded operating systems. Components of an SO: The components of an operating system all exist in order to make the different parts of a computer work together. All user software needs to go through the operating system in order to use any of the hardware, whether it be as simple as a mouse or keyboard or complex as an Internet connection. 1. Kernel: With the aid of the firmware and device drivers, the kernel provides the most basic level of control over all of the computer’s hardware devices.
It manages memory access for programs in the RAM, it determines which programs get access to which reward resources, it sets up or resets the Scup’s operating states for optimal operation at all times, and it organizes the data for long-term non-volatile storage with file systems on such media as disks, tapes, flash memory, etc. 2. Program execution The operating system provides an interface between an application program and the computer hardware, so that an application program can interact with the hardware only by obeying rules and procedures programmed into the operating system.
The operating system is also a set of services which simplify development and execution of application programs. Executing an application program involves the creation of a process by the operating system kernel which assigns memory space and other resources, establishes a priority for the process in multi-tasking systems, loads program binary code into memory, and initiates execution of the application program which then interacts with the user and with hardware devices. 3. Interrupts: Interrupts are central to operating systems, as they provide an efficient way for the operating system to interact with and react to its environment.
The alternative -? having the operating system “watch” the various sources of input for events (polling) hat require action -? can be found in older systems with very small stacks (50 or 60 bytes) but are unusual in modern systems with large stacks. Interrupt-based programming is directly supported by most modern JPL’s. Interrupts provide a computer with a way of automatically saving local register contexts, and running specific code in response to events. Even very basic computers support hardware interrupts, and allow the programmer to specify code which may be run when that event takes place.
When an interrupt is received, the computer’s hardware automatically suspends whatever program is currently running, saves its status, and nuns computer code previously associated with the interrupt; this is analogous to placing a bookmark in a book in response to a phone call. In modern operating systems, interrupts are handled by the operating system’s kernel. Interrupts may come from either the computer’s hardware or from the running program. 4. Modes Modern Cups support multiple modes of operation. Cups with this capability use at least two modes: protected mode and supervisor mode.
The supervisor mode is used by the operating system’s kernel for low level tasks that need unrestricted access to hardware, such as controlling how memory is written and erased, and immunization with devices like graphics cards. Protected mode, in contrast, is used for almost everything else. Applications operate within protected mode, and can only supervisor mode. Cups might have other modes similar to protected mode as well, such as the virtual modes in order to emulate older processor types, such as 16-bit processors on a 32-bit one, or 32-bit processors on a 64-bit one.
When a computer first starts up, it is automatically running in supervisor mode. The first few programs to run on the computer, being the BIOS or EFFIE, boatload, and the operating system eave unlimited access to hardware – and this is required because, by definition, initializing a protected environment can only be done outside of one. However, when the operating system passes control to another program, it can place the CPU into protected mode. 5. Memory management Among other things, a multiprogramming operating system kernel must be responsible for managing all system memory which is currently in use by programs.
This ensures that a program does not interfere with memory already in use by another program. Since programs time share, each program must have independent access to memory. Cooperative memory management, used by many early operating systems, assumes that all programs make voluntary use of the kernel’s memory manager, and do not exceed their allocated memory. This system of memory management is almost never seen any more, since programs often contain bugs which can cause them to exceed their allocated memory.
If a program fails, it may cause memory used by one or more other programs to be affected or overwritten. Malicious programs or viruses may purposefully alter another program’s memory, or may affect the operation of the operating system itself. With cooperative memory management, it takes only one misbehaved program to crash the system. 6. Virtual memory The use of virtual memory addressing (such as paging or segmentation) means that the kernel can choose what memory each program may use at any given time, allowing the operating system to use the same memory locations for multiple tasks.
If a program tries to access memory that isn’t in its current range of accessible memory, but nonetheless has been allocated to it, the kernel will be interrupted in the same way as it would if the program were to exceed its allocated memory. Under UNIX this kind of interrupt is referred to as a page fault. When the kernel detects a page fault it will generally adjust the virtual memory range of the program which triggered it, granting it access to the memory requested.
This gives the kernel discretionary power over where a particular application’s memory is stored, or even whether or not it has actually been allocated yet. 7. Multitasking Multitasking refers to the running of multiple independent computer programs on the same computer; giving the appearance that it is performing the tasks at the same time. Since most computers can do at most one or two things at one time, this is nearly done via time-sharing, which means that each program uses a share of the computer’s time to execute.
An operating system kernel contains a piece of software called a scheduler which determines how much time each program will spend executing, and in which order execution control should be passed to programs. Control is passed to a process by the kernel, which allows the program access to the CPU and memory. Later, control is returned to the kernel through some mechanism, so that another program may be allowed to use the CAP]. This so-called passing of model which governed the allocation of time to programs was called cooperative litigating.
In this model, when control is passed to a program by the kernel, it may execute for as long as it wants before explicitly returning control to the kernel. This means that a malicious or malfunctioning program may not only prevent any other programs from using the CAP], but it can hang the entire system if it enters an infinite loop. Modern operating systems extend the concepts of application preemption to device drivers and kernel code, so that the operating system has preemptive control over internal run-times as well. 8.
Disk access and file systems Access to data stored on disks is a central feature of all operating systems. Computers store data on disks using files, which are structured in specific ways in order to allow for faster access, higher reliability, and to make better use out of the driver’s available space. The specific way in which files are stored on a disk is called a file system, and enables files to have names and attributes. It also allows them to be stored in a hierarchy of directories or folders arranged in a directory tree.
Early operating systems generally supported a single type of disk drive and only one kind of file system. Early file systems were limited in their capacity, speed, and in the kinds f file names and directory structures they could use. These limitations often reflected limitations in the operating systems they were designed for, making it very difficult for an operating system to support more than one file system. While many simpler operating systems support a limited range of options for accessing storage systems, operating systems like UNIX and Linux support a technology known as a virtual file system or VS..
An operating system such as UNIX supports a wide array of storage devices, regardless of their design or file systems, allowing them to be accessed through a common application programming interface (API). This makes it unnecessary for programs to have any knowledge about the device they are accessing. A VS. allows the operating system to provide programs with access to an unlimited number of devices with an infinite variety of file systems installed on them, through the use of specific device drivers and file system drivers. . Device drivers A device driver is a specific type of computer software developed to allow interaction with hardware devices. Typically this constitutes an interface for communicating with the device, through the specific computer bus or communications subsystem that the reward is connected to, providing commands to and/or receiving data from the device, and on the other end, the requisite interfaces to the operating system and software applications.
It is a specialized hardware-dependent computer program which is also operating system specific that enables another program, typically an operating system or applications software package or computer program running under the operating system kernel, to interact transparently with a hardware device, and usually provides the requisite interrupt handling necessary for any necessary asynchronous time-dependent hardware interfacing needs. 10. Networking
Currently most operating systems support a variety of networking protocols, dissimilar operating systems can participate in a common network for sharing resources such as computing, files, printers, and scanners using either wired or wireless connections. Networks can essentially allow a computer’s operating system to access the resources of a remote computer to support the same functions as it could if those resources were connected directly to the local computer.
This includes everything from simple communication, to using networked file systems or even sharing another computer’s graphics or sound hardware. Some network services low the resources of a computer to be accessed transparently, such as SSH which allows networked users direct access to a computer’s command line interface. 11. Security A computer being secure depends on a number of technologies working properly. A modern operating system provides access to a number of resources, which are available to software running on the system, and to external devices like networks via the kernel.
The operating system must be capable of distinguishing between requests which should be allowed to be processed, and others which should not be processed. While some systems may simply distinguish between “privileged” and non-privileged”, systems commonly have a form of requester identity, such as a user name. To establish identity there may be a process of authentication. Often a surname must be quoted, and each surname may have a password. Other methods of authentication, such as magnetic cards or biometric data, might be used instead.
In some cases, especially connections from the network, resources may be accessed with no authentication at all (such as reading files over a network share). Also covered by the concept of requester identity is authorization; the particular services and resources accessible by the requester once logged into a system are died to either the requester’s user account or to the variously configure groups of users to which the requester belongs. 12. User interface Every computer that is to be operated by an individual requires a user interface.
The user interface is not actually a part of the operating system-?it generally runs in a separate program usually referred to as a shell, but is essential if human interaction is to be supported. The user interface requests services from the operating system that will acquire data from input hardware devices, such as a keyboard, mouse or credit card reader, and requests operating system services to display prompts, status assuages and such on output hardware devices, such as a video monitor or printer.
The two most common forms of a user interface have historically been the command- line interface, where computer commands are typed out line-by-line, and the graphical user interface, where a visual environment (most commonly a WIMP) is present. List Operating Systems: * Macros * Subunit * Windows 7 * Bunt * Solaris * Windows XP * Zorn So * Linux Mint * Windows 98 Even after the release Windows 8 Release Preview also most of the Personal Computers (PC’s) and Organizations use Windows XP. And 92. % of Net Market Share of Operating Systems is occupied by Microsoft windows all versions (as on June 2012). Microsoft Windows: Microsoft Windows is a series of graphical interface operating systems developed, marketed, and sold by Microsoft. Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces Microsoft Windows came to dominate the world’s personal computer market, overtaking Mac SO, which had been introduced in 1984.
The most recent client version of Windows is Windows 7; the cost recent server version is Windows Server 2008 RE; the most recent mobile version is Windows Phone 7. 5. Desktop: The screen that appears after Windows loaded is called as DESKTOP. Its general meaning is the working space of a desk is often referred as desktop and in windows too carries the same thing. Desktop is with a background wallpaper and some icons like My Computer, Recycle Bin and so.
On the bottom of desktop we find a bar of color blue with a Start button on its start point and a notification area/tray on the end. In between is called the Task Bar used to control all the opened or minimized programs. Start: Start on the task is comprised of a menu of items to quick access them rather than to go to their original location. Traditionally, the Start menu provided a customizable nested list of programs for the user to launch, as well as a list of most recently opened documents, a way to find files and get help, and access to the system settings.
Later enhancements via Windows Desktop Update included access to special folders like “My Documents” and “Favorites” (browser bookmarks). Windows Asp’s Start menu was expanded to encompass various My Documents folders (including My Music and My Pictures), and transplanted other items like My Computer and My Network Places from the Windows desktop. The Start menu is not a truly essential feature, as programs and files can also be opened by navigating to them in the Windows Explorer interface.
However, the Start menu provides a much quicker and easier way to open programs, even for experienced users, and consolidates a list of programs into one place. Microsoft uses the Start menu more in each version of Windows as a way to shield novice users from the complexities of the operating system. For example, in Windows XP, the root, Program Files and Windows folders are hidden from the user by default, and dated that the Start menu will be retired as of Windows 8 and be replaced by the tablet and touch orientated ‘Start Screen’ based off the new Metro I-Jell.
Figure 3. 03. Start Menu in Windows 7. Figure 3. 04 Apple Menu. Figure 3. 05 KDE Flock Figure 3. 06 Bunt Figure 3. 07 The Linux Mint Cinnamon Start menu Control Panel: The Control Panel is a part of the Microsoft Windows graphical user interface which allows users to view and manipulate basic system settings and controls via applets, such as adding hardware, adding and removing software, controlling user accounts, and changing accessibility options. Additional applets can be provided by third party software.
The Control Panel has been an inherent part of the Microsoft Windows operating system since its first release (Windows 1. 0), with many of the current applets being added in later versions. Beginning with Windows 95, the Control Panel is implemented as a special folder, I. E. The folder does not physically exist, but only contains shortcuts to various applets such as Add or Remove Programs and Internet Options. Physically, these applets are stored as . Cap files. For example, the Add or Remove Programs applet is stored under the name pizza. Cap in the SYSTEM’S folder.
In recent versions of Windows, the Control Panel has two views, Classic View and Category View, and it is possible to switch between these through an option that appears on either the left side or top of the window. Many of the individual Control Panel applets can be accessed in other ways. For instance, Display Properties can be accessed by right-clicking on an empty area of the desktop and choosing Properties. Applet An applet is any small application that performs one specific task that runs within the scope of a larger program, often as a plug-in.
The word Applet was first used in 1990 in PC Magazine. 1 . Accessibility Options (Access. Pl) Allows users to configure the accessibility of their PC. It comprises various settings primarily aimed at users with disabilities or hardware problems. * The behavior of the keyboard can be modified, this is aimed at people who have difficulty pressing key-combinations, or pressing a key Just once. (Stickiness, Filters and Toggles) * Behavior of sounds can be modified. (Soundlessly and Soundness) * High contrast mode can be activated. * The keyboard cursor can be customized. The pointer can be controlled using the keyboard. (MouseKeys) Launches a wizard which allows users to add new hardware devices to the system. This can be done by selecting from a list of devices or by specifying the location of the driver installation files. 3. Add or Remove Programs (pizza. Cap) The Add/Remove Programs dialog allows the user to manipulate software installed on the system in a number of ways; * Allows users to install and change existing software packages, as well as indicating how much space individual programs take and how frequently they are used. Allows users to manually install software from a CD-ROOM or Floppy Disk, and install add-ions from Windows Update. * Allows users to change which Windows components are installed, via the Windows setup Wizard, which includes Internet Explorer, Windows Media Player and Windows Messenger * Finally, it allows users to specify the default applications for certain tasks, via the ‘set program access and defaults’ wizard, such as internet browsers, media players and email programs and whether access to these programs is available 4.
Administrative Tools Contains tools for system administration, including security, performance and service configuration. These are links to various configurations of the Microsoft Management Console such as the local services list and the Event Viewer. 5. Automatic Updates (wakeful. Pl) This is used to specify how the Automatic Updates client (washout. Exe) should download updates from the Microsoft Update Website, by default this is set to download and install daily, however this can be changed to a more suitable frequency.