Computer hardware is a comprehensive term for all physical parts of a computer

Computer hardware is a comprehensive term for all physical parts of a computer, as distinguished from the data it contains or operates on, and the software that provides instructions for the hardware to accomplish tasks. The boundary between hardware and software has become blurred, with the existence of firmware that is software "built into" the hardware. For example, a 2010-era LCD display screen contains a small computer inside. Mass-market consumer computers use highly standardized components and so are simple for an end user to assemble into a working system. Most 2010s-era computers only require users to plug in the power supply, monitor, and other cables. A typical desktop computer consists of a computer case (or "tower"), a metal chassis that holds the power supply , motherboard, hard disk drive , and often an optical disc drive . Most towers have empty space where users can add additional components. External devices such as a computer monitor or visual display unit, keyboard , and a pointing device (mouse) are usually found in a personal computer.
The motherboard connects all processor, memory and peripheral devices together. The RAM, graphics card and processor are in most cases mounted directly onto the motherboard. The central processing unit (microprocessor chip) plugs into a
CPU socket, while the memory modules plug into corresponding memory sockets. Some motherboards have the video display adapter, sound and other peripherals integrated onto the motherboard, while others use expansion slots for graphics cards, network cards, or other I/O devices. The graphics card or sound card may employ a break out box to keep the analog parts away from the
electromagnetic radiation inside the computer case. Disk drives, which provide mass storage, are connected to the motherboard with one cable, and to the power supply through another cable. Usually, disk drives are mounted in the same case as the motherboard; expansion chassis are also made for additional disk storage.
For large amounts of data, a tape drive can be used or extra hard disks can be put together in an external case. The keyboard and the mouse are external devices plugged into the computer through connectors on an I/O panel on the back of the computer case. The monitor is also connected to the input/output (I/O) panel, either through an onboard port on the motherboard, or a port on the graphics card. Capabilities of the personal computers hardware can sometimes be extended by the addition of
expansion cards connected via an expansion bus. Standard peripheral buses often used for adding expansion cards in personal computers include PCI, PCI Express (PCIe), and AGP (a high-speed PCI bus dedicated to graphics adapters, found in older computers). Most modern personal computers have multiple physical PCI Express expansion slots, with some of the having PCI slots as well.
Computer case
Main article: Computer case
An empty ATX case lying on its side
A computer case is an enclosure that contains the main components of a
computer . They are usually constructed from steel or aluminum combined with
plastic , although other materials such as
wood and tempered glass have been used for specialized units. Cases are available in different sizes and shapes; the size and shape of a computer case are usually determined by the configuration of the
motherboard that it is designed to accommodate since this is the largest and most central component of most computers. The most popular style for desktop computers is ATX , although
microATX and similar layouts became very popular for a variety of uses. Companies like Shuttle Inc. and AOpen have popularized small cases, for which
FlexATX is the most common motherboard size. In the 1990s, desktop computer cases were larger and taller than 2010-era computer cases.
Power supply unit
Main article: Power supply unit (computer)
Computer power supply unit with top cover removed
The power supply unit (PSU) converts general-purpose mains AC electricity to
direct current (DC) for the other components of the computer. The rated output capacity of a PSU should usually be about 40% greater than the calculated system power consumption needs to be obtained by adding up all the system components. This protects against overloading the supply, and guards against performance degradation. Power supply capacities range from 250 to 2000
watts for desktop computers.
Processor
Main article: Central processing unit
AMD Athlon 64 X2 CPU
The central processing unit (CPU) is a part of a computer that executes instructions of a software program . In newer PCs, the CPU contains over a million transistors in one integrated circuit chip called the microprocessor. In most cases, the processor plugs directly into the motherboard. The processor chip may have a heat sink and a fan attached for cooling. A large number of computers today [53] are suited to run an x86 -compatible microprocessor[54] manufactured by Intel , AMD , or VIA Technologies.
Motherboard
Main article: Motherboard
A motherboard without processor, memory and expansion cards, cables
The motherboard, also referred to as system board or main board, is the primary circuit board within a personal computer, and other major system components plug directly into it or via a cable. A motherboard contains a microprocessor, the CPU supporting circuitry (mostly integrated circuits ) that provide the interface between 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 or UEFI ). 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.
Main memory
Main article: Primary storage
1 GB DDR SDRAM PC-3200 module
A PC's main memory is a fast primary storage device that is directly accessible by the CPU, and is used to store the currently executing program and immediately needed data. PCs use
semiconductor random-access memory (RAM) of various kinds such as DRAM, SDRAM or SRAM as their primary storage. Which exact kind is used depends on cost/performance issues at any particular time. Main memory is much faster than mass storage devices like hard disk drives or optical discs , but is usually
volatile , meaning that it does not retain its contents (instructions or data) in the absence of power, and is much more expensive for a given capacity than is most mass storage. As a result, main memory is generally not suitable for long-term or archival data storage.
Storage drive
Main article: Hard disk drive
See also: Solid state drive
A 3.5" hard drive with the cover removed.
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 drive . If the mass storage controller provides additional ports 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 ,
SATA and SCSI. Solid state drives (SSDs) are a much faster replacement for traditional mechanical hard disk drives but are also more expensive in terms of cost per gigabyte. Solid state drives connect using several connectors, including SATA, M.2 , and U.2 . Some models use the NVMe protocol, which have vastly improved performance over standard hard disk drives and older SSDs that use the older AHCI protocol.
Visual display unit
Main article: Visual display unit
A visual display unit, computer monitor or just display, is a piece of electrical equipment , usually separate from the computer case, which displays visual
images without producing a permanent computer record. A display device was usually a CRT in the 1980s, but by the 2000s, flat panel displays such as a TFT LCD had largely replaced the bulkier, heavier CRT screens. Multi-monitor setups are quite common in the 2010s, as they enable a user to display multiple programs at the same time (e.g., an email inbox and a word processing program). The display unit houses an electronic circuitry that generates its picture from
signals received from the computer. Within the computer, either integral to the motherboard or plugged into it as an
expansion card, there is pre-processing circuitry to convert the microprocessor's output data to a format compatible with the display unit's circuitry. The images from computer monitors originally contained only text, but as graphical user interfaces emerged and became common, they began to display more images and multimedia content. The term "monitor" is also used, particularly by technicians in broadcasting television, where a picture of the broadcast data is displayed to a highly standardized
reference monitor for confidence checking purposes.
Video card
Main article: Video card
A GTX 1070 video card
The video card—otherwise called a graphics card, graphics adapter or video adapter—processes the graphics output from the motherboard and transmits it to the display. It is an essential part of modern multimedia-enriched computing. Graphics circuitry may be integrated with the motherboard, or may be on cards istalled in PCI, AGP , or PCI Express slots. 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 owing to the limited memory available to the eight-bit processors available at the time.
Keyboard
Main article: Computer keyboard
A "Model M" IBM computer keyboard from the early 1980s. Commonly called the "Clicky Keyboard" due to its buckling spring key spring design, which gives the keyboard its iconic 'click' sound with each keystroke.
A keyboard is an arrangement of buttons that each correspond to a function, letter, or number. They are the primary devices used for inputting text. In most cases, they contain an array 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 keys specific to an operating system. Often, specific functions can be achieved by pressing multiple keys at once or in succession, such as inputting characters with accents or opening a task manager. Programs use keyboard shortcuts 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. In addition to the alphabetic keys found on a typewriter, computer keyboards typically have a numeric keyboard and a row of function keys and special keys, such as CTRL , ALT,
DEL and Esc
Many keyboards include LED lights under the keys that increase the visibility of the letters or symbols in dark environments.
Mouse
Main article: Computer mouse
A selection of computer mice built between 1986 and 2007
A computer mouse is a small handheld device that users hold and slide across a flat surface, pointing at various elements of a graphical user interface with an on-screen cursor, and selecting and moving objects using the mouse buttons. Mice may be plugged into a dedicated mouse socket, or a USB port, or, may be connected wirelessly. Mice include one or more buttons to allow a user to signal the computer to carry out some operation, such as selecting an item from a menu of choices on the screen. A mouse may have a scroll wheel, to allow users to move the displayed image. The scroll wheel can also be pressed down, and used as a third button. Some mouse wheels may be tilted from side to side to allow sideways scrolling. Different programs make use of these functions differently, and may scroll horizontally by default with the scroll wheel, open different menus with different buttons, etc. These functions may be also user-defined through software utilities. Mechanical mice used a ball, which drove pulse generators to detect movement along "north-south" or "east-west" axies. Optical mice use a special mouse pad with a printed grid to allow detection of motion, or else use an imaging chip that allows detection of motion on almost any opaque surface.
Other components
A proper ergonomic design of a personal computer workplace is necessary to prevent repetitive strain injuries, which can develop over time and can lead to long-term disability. [55]
All computers require either fixed or removable storage for their operating system, programs and user-generated material. 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. Initially, the 5.25-inch and 3.5-inch floppy drives 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 forms, became the main method for software distribution, and writeable media provided means for data backup and file interchange. As a result, floppy drives became uncommon in desktop personal computers since about 2000, and were dropped from many laptop systems even earlier.[note 1]
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 is often compatible with several forms of flash memory devices. 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 performs much of the data transfer and backup functions formerly done with floppy drives, Zip disks and other devices. Mainstream operating systems for personal computers provide built-in support for USB flash drives, allowing interchange even between computers with different processors and operating systems. The compact size and lack of moving parts or dirt-sensitive media, combined with low cost and high capacity, have made USB flash drives a popular and useful accessory for any personal computer user.
The operating system can be located on any storage, but is typically installed on a hard disk or solid-state drive. A Live CD represents the concept of running an operating system directly from a CD. While this is slow compared to storing the operating system on a hard disk 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 disk drives of similar size (as of mid-2014) but are starting to appear in laptop computers because of their low weight, small size and low power requirements. Computer communications involve internal modem cards , modems , network adapter cards , and routers. Common peripherals and adapter cards include headsets , joysticks,
microphones , printers, scanners , sound adapter cards (as a separate card rather than located on the motherboard),
speakers and webcams .
Software
Main article: Computer software
A screenshot of the
OpenOffice.org Writer software
Computer software is any kind of
computer program , procedure , or documentation that performs some task on a computer system. [56] The term includes application software such as
word processors that perform productive tasks for users, system software such as
operating systems that interface with
computer hardware to provide the necessary services for application software, and middleware that controls and co-ordinates distributed systems .
Software applications are common for
word processing , Internet browsing,
Internet faxing, e-mail and other digital messaging, multimedia playback, playing of computer game , and computer programming . The user 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.
Operating system
Main article: Operating system
See also: Usage share of operating systems
An operating system (OS) manages computer resources and provides programmers with an interface used to access those resources. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the system. An operating system performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling
input and output devices, facilitating
computer networking, and managing files.
Common contemporary desktop operating systems are Microsoft Windows , macOS , Linux , Solaris and
FreeBSD . Windows, macOS, and Linux all have server and personal variants. With the exception of Microsoft Windows, the designs of each of them were inspired by or directly inherited from the Unix operating system, which was developed at Bell Labs beginning in the late 1960s and spawned the development of numerous free and proprietary operating systems.
Microsoft Windows
Main article: Microsoft Windows
Microsoft Windows is the collective brand name of several operating systems made by Microsoft which, as of 2015, are installed on PCs built by HP, Dell and
Lenovo , the three remaining high volume manufacturers. [57] Microsoft first introduced an operating environment named Windows in November 1985, [58] as an add-on to MS-DOS and in response to the growing interest in graphical user interfaces (GUIs)[59][60] generated by Apple's 1984 introduction of the
Macintosh .[61] As of January 2017, the most recent client and server versions of Windows are Windows 10 and Windows Server 2016 .
macOS
Main article: macOS
macOS (formerly OS X) is a line of
operating systems developed, marketed and sold by Apple Inc. macOS is the successor to the original Mac OS , which had been Apple's primary operating system since 1984. macOS is a Unix-based graphical operating system, and
Snow Leopard, Leopard, Lion , Mountain Lion, Mavericks , Yosemite , El Capitan and
Sierra are its version codenames. The most recent version of macOS is codenamed macOS Mojave .
Linux
Main article: Linux
A Linux distribution running KDE Plasma Workspaces 4
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. [62] The name "Linux" refers to 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. [63]
Known for its use in servers, with the
LAMP application stack as one of prominent examples, 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 , [64] video game systems such as the Steam Machine or PlayStation 3 (until this option was removed remotely by Sony in 2010 [65] ), several arcade games, and
embedded devices such as mobile phones , portable media players , routers , and stage lighting systems.