Computer hardware


Computer hardware comprises the physical parts of a computer, such as the central processing unit (CPU), random access memory (RAM), motherboard, computer data storage, graphics card, sound card, and computer case. It includes external devices such as a monitor, mouse, keyboard, and speakers.[1][2]

PDP-11 CPU board

By contrast, software is the set of instructions that can be stored and run by hardware. Hardware is so-termed because it is hard or rigid with respect to changes, whereas software is soft because it is easy to change.

Hardware is typically directed by the software to execute any command or instruction. A combination of hardware and software forms a usable computing system, although other systems exist with only hardware.



Early computing devices more complicated than the ancient abacus date to the seventeenth century. French mathematician Blaise Pascal designed a gear-based device that could add and subtract, selling around 50 models. The stepped reckoner was invented by Gottfried Leibniz by 1676, which could also divide and multiply. Due to the limitations of contemporary fabrication and design flaws, Leibniz' reckoner was not very functional, but similar devices (Leibniz wheel) remained in use into the 1970s.[3] In the 19th century, Englishman Charles Babbage invented the difference engine, a mechanical device to calculate polynomials for astronomical purposes.[4] Babbage also designed a general-purpose computer that was never built. Much of the design was incorporated into the earliest computers: punch cards for input and output, memory, an arithmetic unit analogous to central processing units, and even a primitive programming language similar to assembly language.[5]

In 1936, Alan Turing developed the universal Turing machine to model any type of computer, proving that no computer would be able to solve the decision problem.[6] The universal Turing machine was a type of stored-program computer capable of mimicking the operations of any Turing machine (computer model) based on the software instructions passed to it. The storage of computer programs is key to the operation of modern computers and is the connection between computer hardware and software.[7] Even prior to this, in the mid-19th century mathematician George Boole invented Boolean algebra—a system of logic where each proposition is either true or false. Boolean algebra is now the basis of the circuits that model the transistors and other components of integrated circuits that make up modern computer hardware.[8] In 1945, Turing finished the design for a computer (the Automatic Computing Engine) that was never built.[9]

Von Neumann architecture scheme

Around this time, technological advancement in relays and vacuum tubes enabled the construction of the first computers.[10] Building on Babbage's design, relay computers were built by George Stibitz at Bell Laboratories and Harvard University's Howard Aiken, who engineered the MARK I.[5] Also in 1945, mathematician John von Neumann—working on the ENIAC project at the University of Pennsylvania—devised the underlying von Neumann architecture that has served as the template for most modern computers.[11] Von Neumann's design featured a centralized memory that stored both data and programs, a central processing unit (CPU) with priority of access to the memory, and input and output units. Von Neumann's solution to the storage problem by locating programs and data adjacent to each other created the Von Neumann bottleneck when the system tries to fetch both at the same time—often throttling the system's performance.[12]

Types of computer systems


Personal computer

Basic hardware components of a personal computer, including a monitor, a motherboard, a CPU, a RAM, two expansion cards, a power supply, an optical disc drive, a hard disk drive, a keyboard and a mouse
Inside a custom-built computer: power supply at the bottom has its own cooling fan

The personal computer is one of the most common types of computer due to its versatility and relatively low price. Desktop personal computers have a monitor, a keyboard, a mouse, and a computer case. The computer case holds the motherboard, fixed or removable disk drives for data storage, the power supply, and may contain other peripheral devices such as modems or network interfaces. Some models of desktop computers integrated the monitor and keyboard into the same case as the processor and power supply. Separating the elements allows the user to arrange the components in a pleasing, comfortable array, at the cost of managing power and data cables between them.

Laptops are designed for portability but operate similarly to desktop PCs.[13] They may use lower-power or reduced size components, with lower performance than a similarly priced desktop computer.[14] Laptops contain the keyboard, display, and processor in one case. The monitor in the folding upper cover of the case can be closed for transportation, to protect the screen and keyboard. Instead of a mouse, laptops may have a touchpad or pointing stick.

Tablets are portable computers that use a touch screen as the primary input device. Tablets generally weigh less and are smaller than laptops.

Some tablets include fold-out keyboards or offer connections to separate external keyboards. Some models of laptop computers have a detachable keyboard, which allows the system to be configured as a touch-screen tablet. They are sometimes called "2-in-1 detachable laptops" or "tablet-laptop hybrids".[15]



A computer case encloses most of the components of a desktop computer system. It provides mechanical support and protection for internal elements such as the motherboard, disk drives, and power supply, and controls and directs the flow of cooling air over internal components. The case is also part of the system to control electromagnetic interference radiated by the computer and protects internal parts from electrostatic discharge. Large tower cases provide space for multiple disk drives or other peripherals and usually stand on the floor, while desktop cases provide less expansion room. All-in-one style designs include a video display built into the same case. Portable and laptop computers require cases that provide impact protection for the unit. Hobbyists may decorate the cases with colored lights, paint, or other features, in an activity called case modding.

Power supply


A power supply unit (PSU) converts alternating current (AC) electric power to low-voltage direct current (DC) power for the computer. The PSU typically uses a switched-mode power supply (SMPS), with power MOSFETs (power metal–oxide–semiconductor field-effect transistors) used in the converters and regulator circuits of the SMPS.[16]

Laptops can run on a built-in rechargeable battery.[17]


Computer motherboard

The motherboard is the main component of a computer. It is a board with integrated circuitry that connects the other parts of the computer including the CPU, the RAM, the disk drives (CD, DVD, hard disk, or any others) as well as any peripherals connected via the ports or the expansion slots. The integrated circuit (IC) chips in a computer typically contain billions of tiny metal–oxide–semiconductor field-effect transistors (MOSFETs).[18]

Components directly attached to or to part of the motherboard include:

Expansion cards


An expansion card in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard or backplane to add functionality to a computer system via the expansion bus. Expansion cards can be used to obtain or expand on features not offered by the motherboard.

Storage devices


A storage device is computer hardware or digital media that is used for storing, porting, and extracting data files and objects. It can hold and store information either temporarily or permanently and can be internal or external to a computer. Data storage is a core function and fundamental component of computers. Dedicated storage devices include RAIDs and tape libraries.

Fixed media

Data is stored by a computer using a variety of media. Hard disk drives (HDDs) are found in virtually all older computers, due to their high capacity and low cost, but solid-state drives (SSDs) are faster and more power efficient, although currently more expensive than hard drives in terms of dollar per gigabyte,[19] so are often found in personal computers built post-2007.[20] SSDs use flash memory, which stores data on MOS memory chips consisting of floating-gate MOSFET memory cells. Some systems may use a disk array controller for greater performance or reliability.

Removable media

To transfer data between computers, an external flash memory device (such as a memory card or USB flash drive) or optical disc (such as a CD-ROM, DVD-ROM or BD-ROM) may be used. Their usefulness depends on being readable by other systems; the majority of machines have an optical disk drive (ODD), and virtually all have at least one Universal Serial Bus (USB) port. USB sticks are typically pre-formatted with the FAT32 file system, which is widely supported across operating systems.

Input and output peripherals


Input and output devices are typically housed externally to the main computer chassis. The following are either standard or very common to many computer systems.

Input device

Input devices allow the user to enter information into the system, or control its operation. Most personal computers have a mouse and keyboard, but laptop systems typically use a touchpad instead of a mouse. Other input devices include webcams, microphones, joysticks, and image scanners.

Output device

Output devices are designed around the senses of human beings. For example, monitors display text that can be read, speakers produce sound that can be heard.[21] Such devices also could include printers or a Braille embosser.

Mainframe computer


A mainframe computer is a much larger computer that typically fills a room and may cost many hundreds or thousands of times as much as a personal computer. They are designed to perform large numbers of calculations for governments and large enterprises.

An IBM System z9 mainframe

Departmental computing


In the 1960s and 1970s, more and more departments started to use cheaper and dedicated systems for specific purposes like process control and laboratory automation. A minicomputer, or colloquially mini, is a class of smaller computers that was developed in the mid-1960s[22][23] and sold for much less than mainframe[24] and mid-size computers from IBM and its direct competitors.



A supercomputer is superficially similar to a mainframe but is instead intended for extremely demanding computational tasks. As of November 2021, the fastest supercomputer on the TOP500 supercomputer list is Fugaku, in Japan, with a LINPACK benchmark score of 415 PFLOPS, superseding the second fastest, Summit, in the United States, by around 294 PFLOPS.

The term supercomputer does not refer to a specific technology. Rather it indicates the fastest computations available at any given time. In mid-2011, the fastest supercomputers boasted speeds exceeding one petaflop, or 1 quadrillion (10^15 or 1,000 trillion) floating-point operations per second. Supercomputers are fast but extremely costly, so they are generally used by large organizations to execute computationally demanding tasks involving large data sets. Supercomputers typically run military and scientific applications. Although costly, they are also being used for commercial applications where huge amounts of data must be analyzed. For example, large banks employ supercomputers to calculate the risks and returns of various investment strategies, and healthcare organizations use them to analyze giant databases of patient data to determine optimal treatments for various diseases and problems incurring to the country.

Hardware upgrade


When using computer hardware, an upgrade means adding new or additional hardware to a computer that improves its performance, increases its capacity, or adds new features. For example, a user could perform a hardware upgrade to replace the hard drive with a faster one or a solid-state drive (SSD) to get a boost in performance. The user may also install more random-access memory (RAM) so the computer can store additional temporary data, or retrieve such data at a faster rate. The user may add a USB 3.0 expansion card to fully use USB 3.0 devices, or could upgrade the graphics processing unit (GPU) for cleaner, more advanced graphics, or more monitors. Performing such hardware upgrades may be necessary for aged computers to meet a new, or updated program's system requirements.

In large organizations, hardware upgrades are handled by administrators who are also in charge of keeping networks running smoothly. They replace network devices like servers, routers and storage devices based on new demands and capacities.



Global revenue from computer hardware in 2023 reached $705.17 billion.[25]



Because computer parts contain hazardous materials, there is a growing movement to recycle old and outdated parts.[26] Computer hardware contain dangerous chemicals such as lead, mercury, nickel, and cadmium. According to the EPA these e-wastes have a harmful effect on the environment unless they are disposed of properly. Making hardware requires energy, and recycling parts will reduce air pollution, water pollution, as well as greenhouse gas emissions.[27] Disposing unauthorized computer equipment is in fact illegal. Legislation makes it mandatory to recycle computers through the government approved facilities. Recycling a computer can be made easier by taking out certain reusable parts. For example, the RAM, DVD drive, the graphics card, hard drive or SSD, and other similar removable parts can be reused.

Many materials used in computer hardware can be recovered by recycling for use in future production. Reuse of tin, silicon, iron, aluminum, and a variety of plastics that are present in bulk in computers or other electronics can reduce the costs of constructing new systems. Components frequently contain copper, gold, tantalum,[28][29] silver, platinum, palladium, and lead as well as other valuable materials suitable for reclamation.[30][31]

Toxic computer components


The central processing unit contains many toxic materials. It contains lead and chromium in the metal plates. Resistors, semiconductors, infrared detectors, stabilizers, cables, and wires contain cadmium. The circuit boards in a computer contain mercury, and chromium.[32] When these types of materials, and chemicals are disposed improperly will become hazardous for the environment.

Environmental effects


According to the United States Environmental Protection Agency only around 15% of the e-waste actually is recycled. When e-waste byproducts leach into groundwater, are burned, or get mishandled during recycling, it causes harm. Health problems associated with such toxins include impaired mental development, cancer, and damage to the lungs, liver, and kidneys.[33] That is why even wires have to be recycled. Different companies have different techniques to recycle a wire. The most popular one is the grinder that separates the copper wires from the plastic/rubber casing. When the processes are done there are two different piles left; one containing the copper powder, and the other containing plastic/rubber pieces.[34] Computer monitors, mice, and keyboards all have a similar way of being recycled. For example, first, each of the parts are taken apart then all of the inner parts get separated and placed into its own bin.[35]

Computer components contain many toxic substances, like dioxins, polychlorinated biphenyls (PCBs), cadmium, chromium, radioactive isotopes and mercury. Circuit boards contain considerable quantities of lead-tin solders that are more likely to leach into groundwater or create air pollution due to incineration. In US landfills, about 40% of the lead content levels are from e-waste.[36] The processing (e.g. incineration and acid treatments) required to reclaim these precious substances may release, generate, or synthesize toxic byproducts.

Recycling of computer hardware is considered environmentally friendly because it prevents hazardous waste, including heavy metals and carcinogens, from entering the atmosphere, landfill or waterways. While electronics consist a small fraction of total waste generated, they are far more dangerous. There is stringent legislation designed to enforce and encourage the sustainable disposal of appliances, the most notable being the Waste Electrical and Electronic Equipment Directive of the European Union and the United States National Computer Recycling Act.[37]

Efforts for minimizing computer hardware waste


As computer hardware contain a wide number of metals inside, the United States Environmental Protection Agency (EPA) encourages the collection and recycling of computer hardware. "E-cycling", the recycling of computer hardware, refers to the donation, reuse, shredding and general collection of used electronics. Generically, the term refers to the process of collecting, brokering, disassembling, repairing and recycling the components or metals contained in used or discarded electronic equipment, otherwise known as electronic waste (e-waste). "E-cyclable" items include, but are not limited to: televisions, computers, microwave ovens, vacuum cleaners, telephones and cellular phones, stereos, and VCRs and DVDs just about anything that has a cord, light or takes some kind of battery.[38]

Some companies, such as Dell and Apple, will recycle computers of their make or any other make. Otherwise, a computer can be donated to Computer Aid International which is an organization that recycles and refurbishes old computers for hospitals, schools, universities, etc.[39]

See also



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  2. ^ Gilster, Ron (2001). PC hardware : a beginner's guide. Internet Archive. New York; London : McGraw-Hill. ISBN 978-0-07-212990-8.
  3. ^ Blum 2011, p. 13-14.
  4. ^ Blum 2011, p. 14.
  5. ^ a b Blum 2011, p. 15.
  6. ^ Blum 2011, pp. 21, 23.
  7. ^ Blum 2011, p. 25.
  8. ^ Blum 2011, pp. 34–35.
  9. ^ Blum 2011, pp. 71–72.
  10. ^ Blum 2011, p. 72.
  11. ^ Blum 2011, pp. 72, 74.
  12. ^ Blum 2011, p. 74.
  13. ^ PC hardware : a beginner's guide. Osborne/McGraw-Hill. 26 April 2001. pp. 21. ISBN 9780072129908.
  14. ^ "Desktop computer vs. Laptop computer". Computer Hope. 30 December 2019. Retrieved 15 January 2020.
  15. ^ Cipriani, Jason (29 May 2020). "Best 2-in-1 Detachable Laptops 2020: The Best Tablet-Laptop Hybrids". IGN. Retrieved 20 July 2020.
  16. ^ a b Harding, Scharon (17 September 2019). "What Is a MOSFET? A Basic Definition". Tom's Hardware. Retrieved 7 November 2019.
  17. ^ "How long should a laptop battery last?". Computer Hope. Archived from the original on 21 December 2013. Retrieved 9 December 2013.
  18. ^ "13 Sextillion & Counting: The Long & Winding Road to the Most Frequently Manufactured Human Artifact in History". Computer History Museum. 2 April 2018. Retrieved 28 July 2019.
  19. ^ Domingo, Joel. "SSD vs. HDD: What's the Difference?". PCMag. Archived from the original on 19 March 2017. Retrieved 24 March 2017.
  20. ^ Edwards, Benj (17 January 2012). "Evolution of the Solid-State Drive". PCWorld. Archived from the original on 25 March 2017. Retrieved 24 March 2017.
  21. ^ PC hardware : a beginner's guide. Osborne/McGraw-Hill. 2001. pp. 20. ISBN 9780072129908.
  22. ^ Henderson, Rebecca M.; Newell, Richard G., eds. (2011). Accelerating energy innovation : insights from multiple sectors. Chicago: University of Chicago Press. p. 180. ISBN 978-0226326832.
  23. ^ Huang, Han-Way (2014). The atme AVR microcontroller : MEGA and XMEGA in assembly and C. Australia; United Kingdom: Delmar Cengage Learning. p. 4. ISBN 978-1133607298.
  24. ^ Estabrooks, Maurice (1995). Electronic technology, corporate strategy, and world transformation. Westport, Conn.: Quorum Books. p. 53. ISBN 0899309690.
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  26. ^ "How to recycle your old computer". Digital Trends. 18 December 2016. Archived from the original on 17 April 2017. Retrieved 18 April 2017.
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  28. ^ Robert-Tissot, Sarah (2011). "TANTALUM". Royal Australian Chemical Institute. Archived from the original on 26 February 2017. Retrieved 3 March 2019.
  29. ^ Padilla, Abraham (February 2019). "TANTALUM" (PDF). United states geological survey. Retrieved 3 March 2019.
  30. ^ Bleiwas, D (July 2001). "Obsolete Computers, "Gold Mine," or High-Tech Trash? Resource Recovery from Recycling" (PDF). USGS. Retrieved 4 March 2019.
  31. ^ LeBlanc, Rick. "Electronic Devices a Rich Source of Precious Metals for Recyclers". The Balance Small Business. Retrieved 4 March 2019.
  32. ^ "The Toxic Components of Computers and Monitors". Archived from the original on 27 April 2017. Retrieved 26 April 2017.
  33. ^ "What's Going On with Electronic Waste? – Electronics TakeBack Coalition". Archived from the original on 27 April 2017. Retrieved 26 April 2017.
  34. ^ "Wire Recycling". Archived from the original on 10 July 2017. Retrieved 5 May 2017.
  35. ^ "Computer equipment recycling – Essential Guide". ComputerWeekly. Archived from the original on 21 December 2016. Retrieved 8 May 2017.
  36. ^ Toothman, Jessika (2 June 2008). "What Happens to your Discarded Old Computer?". HowStuffWorks.
  37. ^ National Computer Recycling Act of 2005, H.R. 425, 109th Cong. (2005–2006)
  38. ^ T. Gallo, Daniel (15 July 2013). "Broad Overview of E-Waste Management Policies in the U.S." (PDF). Retrieved 17 January 2020.
  39. ^ Schofield, Jack (19 February 2015). "How can I safely recycle my old PCs?". The Guardian. ISSN 0261-3077. Archived from the original on 27 April 2017. Retrieved 26 April 2017.


  • Blum, Edward K. (2011). Computer Science: The Hardware, Software and Heart of It. Springer Science & Business Media. ISBN 978-1-4614-1168-0.
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