KDE 4 running on a Linux distribution.

Linux is a family of Unix-like computer operating systems. Linux is one of the most prominent examples of free software and open source development: typically all underlying source code can be freely modified, used, and redistributed by anyone.[28] The name “Linux” comes from the Linux kernel, started in 1991 by Linus Torvalds. The system’s utilities and libraries usually come from the GNU operating system, announced in 1983 by Richard Stallman. The GNU contribution is the basis for the alternative name GNU/Linux.[29]

Known for its use in servers as part of the LAMP application stack, Linux is supported by corporations such as Dell, Hewlett-Packard, IBM, Novell, Oracle Corporation, Red Hat, Canonical Ltd. and Sun Microsystems. It is used as an operating system for a wide variety of computer hardware, including desktop computers, netbooks, supercomputers,[30] video game systems, such as the PlayStation 3, several arcade games, and embedded devices such as mobile phones, portable media players, routers, and stage lighting systems.

A screenshot of the OpenOffice.org Writer software

Computer software is a general term used to describe a collection of computer programs, procedures and documentation that perform some tasks on a computer system.[22] The term includes application software such as word processors which perform productive tasks for users, system software such as operating systems, which interface with hardware to provide the necessary services for application software, and middleware which controls and co-ordinates distributed systems.

Software applications for word processing, Internet browsing, Internet faxing, e-mail and other digital messaging, multimedia playback, computer game play and computer programming are common. The user of a modern personal computer may have significant knowledge of the operating environment and application programs, but is not necessarily interested in programming nor even able to write programs for the computer. Therefore, most software written primarily for personal computers tends to be designed with simplicity of use, or “user-friendliness” in mind. However, the software industry continuously provide a wide range of new products for use in personal computers, targeted at both the expert and the non-expert user.

Mass storage

All computers require either fixed or removable storage for their operating system, programs and user generated material.
Formerly the 5 1/4 inch and 3 1/2 inch floppy drive were the principal forms of removable storage for backup of user files and distribution of software.

As memory sizes increased, the capacity of the floppy did not keep pace; the Zip drive and other higher-capacity removable media were introduced but never became as prevalent as the floppy drive.

By the late 1990s the optical drive, in CD and later DVD and Blu-ray Disc, became the main method for software distribution, and writeable media provided backup and file interchange. Floppy drives have become uncommon in desktop personal computers since about 2000, and were dropped from many laptop systems even earlier. [21]

Early home computers used compact audio cassettes for file storage; these were at the time a very low cost storage solution, but were displaced by floppy disk drives when manufacturing costs dropped, by the mid 1980s.

A second generation of tape recorders was provided when Videocassette recorders were pressed into service as backup media for larger disk drives. All these systems were less reliable and slower than purpose-built magnetic tape drives. Such tape drives were uncommon in consumer-type personal computers but were a necessity in business or industrial use.

Interchange of data such as photographs from digital cameras is greatly expedited by installation of a card reader, which often is compatible with several forms of flash memory. It is usually faster and more convenient to move large amounts of data by removing the card from the mobile device, instead of communicating with the mobile device through a USB interface.

A USB flash drive today performs much of the data transfer and backup functions formerly done with floppy drives, Zip disks and other devices. Main-stream current operating systems for personal computers provide standard support for flash drives, allowing interchange even between computers using different processors and operating systems. The compact size and lack of moving parts or dirt-sensitive media, combined with low cost for high capacity, have made flash drives a popular and useful accessory for any personal computer user.

The operating system (e.g.: Microsoft Windows, Mac OS, Linux or many others) can be located on any storage, but typically it is on a hard disks. A Live CD is the running of a OS directly from a CD. While this is slow compared to storing the OS on a hard drive, it is typically used for installation of operating systems, demonstrations, system recovery, or other special purposes. Large flash memory is currently more expensive than hard drives of similar size (as of mid-2008) but are starting to appear in laptop computers because of their low weight, small size and low power requirements.

Computer communications

* Internal modem card
* Modem
* Network adapter card
* Router

Common peripherals and adapter cards

* Headset
* Joystick
* Microphone
* Printer
* Scanner
* Sound adapter card as a separate card rather than located on the motherboard
* Speakers
* Webcam

Apple Mighty Mouse that detects clicks through a large button located at the bottom of the mouse covering the entire unit.

A Mouse on a computer is a small, slidable device that users hold and slide around to point at, click, and sometimes drag objects on screen in a graphical user interface using a pointer on screen. Almost all Personal Computers have mice. It may be plugged into a computer’s rear mouse socket, or as a USB device, or, more recently, may be connected wirelessly via a USB antenna or Bluetooth antenna. In the past, they had a single button that users could press down on the device to “click” on whatever the pointer on the screen was hovering over. Now, however, many Mice have two or three buttons; a “right click” function button on the mouse, which performs a secondary action on a selected object, and a scroll wheel, which users can rotate the wheel using their fingers to “scroll” up or down. The scroll wheel can also be pressed down, and therefore be used as a third button. Different programs make use of these functions differently, and may scroll horizontally by default with the scroll wheel, open different menus with different buttons, among others.

Mice traditionally detected movement and communicated with the computer with an internal “mouse ball”; and use optical encoders to detect rotation of the ball and tell the computer where the mouse has moved. However, these systems were subject to low durability and accuracy. Modern mice use optical technology to directly trace movement of the surface under the mouse and are much more accurate and durable. They work on a wider variety of surfaces and can even operate on walls, ceilings or other non-horizontal surfaces.

In computing, a keyboard is an arrangement of buttons that each correspond to a function, letter, or number. They are the primary devices of inputing text. In most cases, they contain an aray of keys specifically organized with the corresponding letters, numbers, and functions printed or engraved on the button. They are generally designed around an operators language, and many different versions for different languages exist. In English, the most common layout is the QWERTY layout, which was originally used in typewriters. They have evolved over time, and have been modified for use in computers with the addition of function keys, number keys, arrow keys, and OS specific keys. Often, specific functions can be achieved by pressing multiple keys at once or in succession, such as inputing characters with accents or opening a task manager. Programs use keyboard shotcuts very differently and all use different keyboard shortcuts for different program specific operations, such as refreshing a web page in a web browser or selecting all text in a word processor.

The video card – otherwise called a graphics card, graphics adapter or video adapter – processes and renders the graphics output from the computer to the computer display, and is an essential part of the modern computer. On older models, and today on budget models, graphics circuitry tended to be integrated with the motherboard but, for modern flexible machines, they are supplied in PCI, AGP, or PCI Express format.

When the IBM PC was introduced, most existing business-oriented personal computers used text-only display adapters and had no graphics capability. Home computers at that time had graphics compatible with television signals, but with low resolution by modern standards owing to the limited memory available to the eight-bit processors available at the time.

Mass storage devices store programs and data even when the power is off; they do require power to perform read and write functions during usage. Although flash memory has dropped in cost, the prevailing form of mass storage in personal computers is still the hard disk.

The disk drives use a sealed head/disk assembly (HDA) which was first introduced by IBM’s “Winchester” disk system. The use of a sealed assembly allowed the use of positive air pressure to drive out particles from the surface of the disk, which improves reliability.

If the mass storage controller provides for expandability, a PC may also be upgraded by the addition of extra hard disk or optical disc drives. For example, BD-ROMs, DVD-RWs, and various optical disc recorders may all be added by the user to certain PCs. Standard internal storage device connection interfaces are PATA, Serial ATA, SCSI

The motherboard, also referred to as systemboard or mainboard, is the primary circuit board within a personal computer. Many other components connect directly or indirectly to the motherboard. Motherboards usually contain one or more CPUs, supporting circuitry – usually integrated circuits (ICs) – providing the interface between the CPU memory and input/output peripheral circuits, main memory, and facilities for initial setup of the computer immediately after power-on (often called boot firmware or, in IBM PC compatible computers, a BIOS). In many portable and embedded personal computers, the motherboard houses nearly all of the PC’s core components. Often a motherboard will also contain one or more peripheral buses and physical connectors for expansion purposes. Sometimes a secondary daughter board is connected to the motherboard to provide further expandability or to satisfy space constraints.

1. Scanner
2. CPU (Microprocessor)
3. Primary storage (RAM)
4. Expansion cards (graphics cards, etc)
5. Power supply
6. Optical disc drive
7. Secondary storage (Hard disk)
8. Motherboard
9. Speakers
10. Monitor
11. System software
12. Application software
13. Keyboard
14. Mouse
15. External hard disk
16. Printer

Main article: Computer hardware

A typical hardware setup of a desktop computer consists of:

* computer case with power supply
* central processing unit (processor)
* motherboard
* memory card
* hard disk
* video card
* visual display unit (monitor)
* optical disc (usually DVD-ROM or DVD Writer)
* keyboard and pointing device

These components can usually be put together with little knowledge to build a computer. The motherboard is a main part of a computer that connects all devices together. The memory card(s), graphics card and processor are mounted directly onto the motherboard (the processor in a socket and the memory and graphics cards in expansion slots). The mass storage is connected to it with cables and can be installed in the computer case or in a separate case. This is the same for the keyboard and mouse, except that they are external and connect to the I/O panel on the back of the computer. The monitor is also connected to the I/O panel, either through an onboard port on the motherboard, or a port on the graphics card.

Several functions (implemented by chipsets) can be integrated into the motherboard, typically USB and network, but also graphics and sound. Even if these are present, a separate card can be added if what is available isn’t sufficient. The graphics and sound card can have a break out box to keep the analog parts away from the electromagnetic radiation inside the computer case. For really large amounts of data, a tape drive can be used or (extra) hard disks can be put together in an external case.

The hardware capabilities of personal computers can sometimes be extended by the addition of expansion cards connected via an expansion bus. Some standard peripheral buses often used for adding expansion cards in personal computers as of 2005 are PCI, AGP (a high-speed PCI bus dedicated to graphics adapters), and PCI Express. Most personal computers as of 2005 have multiple physical PCI expansion slots. Many also include an AGP bus and expansion slot or a PCI Express bus and one or more expansion slots, but few PCs contain both buses.

A tablet PC is a notebook or slate-shaped mobile computer, first introduced by Pen computing in the early 90s with their PenGo Tablet Computer and popularized by Microsoft. Its touchscreen or graphics tablet/screen hybrid technology allows the user to operate the computer with a stylus or digital pen, or a fingertip, instead of a keyboard or mouse. The form factor offers a more mobile way to interact with a computer. Tablet PCs are often used where normal notebooks are impractical or unwieldy, or do not provide the needed functionality.

As technology and functionality continue to progress, prototype tablet PC’s will continue to emerge. The Microsoft Courier, a personal business device, has two 7″ monitors that support multi-touch gestures, Wi-Fi capabilities and has a built-in camera. The device looks to be a replacement to traditional planners while offering what most digital planners cannot, two pages and large writing spaces. [17]