Computer hardware

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PDP-11 CPU board PDP-11-M7270.jpg
PDP-11 CPU board

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

Contents

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.

Von Neumann architecture

Von Neumann architecture scheme Von Neumann Architecture.svg
Von Neumann architecture scheme

The template for all modern computers is the Von Neumann architecture, detailed in a 1945 paper by Hungarian mathematician John von Neumann. This describes a design architecture for an electronic digital computer with subdivisions of a processing unit consisting of an arithmetic logic unit and processor registers, a control unit containing an instruction register and program counter, a memory to store both data and instructions, external mass storage, and input and output mechanisms. [3] The meaning of the term has evolved to mean a stored-program computer in which an instruction fetch and a data operation cannot occur at the same time because they share a common bus. This is referred to as the Von Neumann bottleneck and often limits the performance of the system. [4]

Types of computer systems

Personal computer

Basic hardware components of a modern 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 Personal computer, exploded 6.svg
Basic hardware components of a modern 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 Computer from inside 018.jpg
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. [1] They may use lower-power or reduced size components, with lower performance than a similarly priced desktop computer. [5] 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 trackpad or pointing stick.

Tablets are portable computer that uses 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". [6]

Case

The computer case encloses most of the components of the system. It provides mechanical support and protection for internal elements such as the motherboard, disk drives, and power supplies, 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. Laptops can run on built-in rechargeable battery. [7] 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. [8]

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). [9]

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 any computing hardware and digital media that is used for storing, porting and extracting data files and objects. It can hold and store information both temporarily and permanently and can be internal or external to a computer, server or any similar computing device. Data storage is a core function and fundamental component of computers.

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, [10] so are often found in personal computers built post-2007. [11] 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.

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. [12] 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 Front Z9 2094.jpg
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 [13] [14] and sold for much less than mainframe [15] and mid-size computers from IBM and its direct competitors.

Supercomputer

A supercomputer is superficially similar to a mainframe but is instead intended for extremely demanding computational tasks. As of June 2018, the fastest supercomputer on the TOP500 supercomputer list is the Summit, in the United States, with a LINPACK benchmark score of 122.3 PFLOPS Light, by around 29 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.

Sales

Global revenue from computer hardware in 2016 reached 408 billion Euros. [16]

Recycling

Because computer parts contain hazardous materials, there is a growing movement to recycle old and outdated parts. [17] 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. [18] 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, aluminium, 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, [19] [20] silver, platinum, palladium, and lead as well as other valuable materials suitable for reclamation. [21] [22]

Toxic computer components

The central processing unit contains many toxic materials. It contains lead and chromium in the metal plates. Resistors, semi-conductors, infrared detectors, stabilizers, cables, and wires contain cadmium. The circuit boards in a computer contain mercury, and chromium. [23] 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. [24] That's 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. [25] 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. [26]

Computer components contain many toxic substances, like dioxins, polychlorinated biphenyls (PCBs), cadmium, chromium, radioactive isotopes and mercury. A typical computer monitor may contain more than 6% lead by weight, much of which is in the lead glass of the cathode ray tube (CRT). A typical 15 inch (38 cm) computer monitor may contain 1.5 pounds (1 kg) of lead [27] but other monitors have been estimated to have up to 8 pounds (4 kg) of lead. [28] 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. [29] 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. [30]

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. [31]

Recycling a computer is made easier by a few of the national services, such as Dell and Apple. Both companies will take back the computer 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. [32]

See also

Related Research Articles

BIOS Firmware

BIOS is firmware used to perform hardware initialization during the booting process, and to provide runtime services for operating systems and programs. The BIOS firmware comes pre-installed on a personal computer's system board, and it is the first software to run when powered on. The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS originally proprietary to the IBM PC has been reverse engineered by companies looking to create compatible systems. The interface of that original system serves as a de facto standard.

Industry Standard Architecture 16-bit internal bus of IBM PC/AT

Industry Standard Architecture (ISA) is the 16-bit internal bus of IBM PC/AT and similar computers based on the Intel 80286 and its immediate successors during the 1980s. The bus was (largely) backward compatible with the 8-bit bus of the 8088-based IBM PC, including the IBM PC/XT as well as IBM PC compatibles.

Motherboard main printed circuit board (PCB) for a computing device

A motherboard is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems, such as the central processor, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general use.

Desktop computer Computer designed to be used on a fixed location

A desktop computer is a personal computer designed for regular use at a single location on or near a desk or table due to its size and power requirements. The most common configuration has a case that houses the power supply, motherboard (a printed circuit board with a microprocessor as the central processing unit, memory, bus, and other electronic components, disk storage ; a keyboard and mouse for input; and a computer monitor, speakers, and, often, a printer for output. The case may be oriented horizontally or vertically and placed either underneath, beside, or on top of a desk.

Workstation High-end computer designed for technical or scientific applications

A workstation is a special computer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems. The term workstation has also been used loosely to refer to everything from a mainframe computer terminal to a PC connected to a network, but the most common form refers to the class of hardware offered by several current and defunct companies such as Sun Microsystems, Silicon Graphics, Apollo Computer, DEC, HP, NeXT and IBM which opened the door for the 3D graphics animation revolution of the late 1990s.

Commodore PET home computer

The Commodore PET is a line of home/personal computers produced starting in 1977 by Commodore International. The system combined a MOS 6502 microprocessor, Commodore BASIC in read only memory (ROM), a keyboard, a computer monitor and a cassette deck for data and program storage in a single all-in-one case.

Video card expansion card which generates a feed of output images to a display

A video card is an expansion card which generates a feed of output images to a display device. Frequently, these are advertised as discrete or dedicated graphics cards, emphasizing the distinction between these and integrated graphics. At the core of both is the graphics processing unit (GPU), which is the main part that does the actual computations, but should not be confused with the video card as a whole, although "GPU" is often used as a metonymic shorthand to refer to video cards.

Overclocking Practice of increasing the clock rate of a computer to exceed that certified by the manufacturer

In computing, overclocking is the practice of increasing the clock rate of a computer to exceed that certified by the manufacturer. Commonly, operating voltage is also increased to maintain a component's operational stability at accelerated speeds. Semiconductor devices operated at higher frequencies and voltages increase power consumption and heat. An overclocked device may be unreliable or fail completely if the additional heat load is not removed or power delivery components cannot meet increased power demands. Many device warranties state that overclocking and/or over-specification voids any warranty, however there are an increasing number of manufacturers that will allow overclocking as long as performed (relatively) safely.

Laptop Personal computer for mobile use

A laptop, is a small, portable personal computer (PC) with a "clamshell" form factor, typically having a thin LCD or LED computer screen mounted on the inside of the upper lid of the clamshell and an alphanumeric keyboard on the inside of the lower lid. The clamshell is opened up to use the computer. Laptops are folded shut for transportation, and thus are suitable for mobile use. Its name comes from lap, as it was deemed to be placed on a person's lap when being used. Although originally there was a distinction between laptops and notebooks, as of 2014, there is often no longer any difference. Today, laptops are commonly used in a variety of settings, such as at work, in education, for playing games, web browsing, for personal multimedia, and general home computer use.

A quiet PC is a personal computer that makes very little or no noise. Common uses for quiet PCs include video editing, sound mixing and home theater PCs, but noise reduction techniques can also be used to greatly reduce the noise from servers. There is currently no standard definition for a "quiet PC", and the term is generally not used in a business context, but by individuals and the businesses catering to them.

A custom-built or homebuilt computer is a computer assembled from available components, usually commercial off-the-shelf (COTS) components, rather than purchased as a complete system from a computer system supplier, also known as pre-built systems.

Gaming computer Desktop or laptop computer meant for running demanding video games and other applications

A gaming computer, also known as a gaming PC or gaming rig, is a personal computer designed for playing video games that require a high amount of computing power. A modern gaming computer is comparable to a mainstream computer with the addition of performance-oriented components, such as high-performance video cards and high core-count central processing units, that sacrifice power efficiency for raw performance. Gaming computers are often associated with enthusiast computing due to an overlap in interests; however, while a gaming computer is built to achieve performance for actual gameplay, enthusiast PCs are built to maximize performance, using games as a real application benchmark. Whereas enthusiast PCs are high-end by definition, gaming PCs can be subdivided into low-end, mid-range, and high-end markets. Video card manufacturers earn the bulk of their revenue from their low-end and mid-range offerings. Gaming PCs are often also suitable for other intensive tasks, like video editing.

Enthusiast computing refers to a sub-culture of personal computer users who focus on extremely high-end computers. Manufacturers of performance-oriented parts typically include an enthusiast model in their offerings. Enthusiast computers commonly feature extravagant cases and high-end components, and are sometimes liquid cooled.

A computer is a machine that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming. Modern computers have the ability to follow generalized sets of operations, called programs. These programs enable computers to perform an extremely wide range of tasks. A "complete" computer including the hardware, the operating system, and peripheral equipment required and used for "full" operation can be referred to as a computer system. This term may as well be used for a group of computers that are connected and work together, in particular a computer network or computer cluster.

The history of the personal computer as a mass-market consumer electronic device began with the microcomputer revolution of the 1970s. A personal computer is one intended for interactive individual use, as opposed to a mainframe computer where the end user's requests are filtered through operating staff, or a time-sharing system in which one large processor is shared by many individuals. After the development of the microprocessor, individual personal computers were low enough in cost that they eventually became affordable consumer goods. Early personal computers – generally called microcomputers – were sold often in electronic kit form and in limited numbers, and were of interest mostly to hobbyists and technicians.

History of laptops aspect of history

The history of laptops describes the efforts, begun in the 1970s, to build small, portable personal computers that combine the components, inputs, outputs and capabilities of a desktop computer in a small chassis.

Personal computer Computer intended for use by an individual person

A personal computer (PC) is a multi-purpose computer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or technician. Unlike large, costly minicomputers and mainframes, time-sharing by many people at the same time is not used with personal computers.

GPU switching

GPU switching is a mechanism used on computers with multiple graphic controllers. This mechanism allows the user to either maximize the graphic performance or prolong battery life by switching between the graphic cards. It's mostly used on gaming laptops which usually have an integrated graphic device and a discrete video card.

This glossary of computer hardware terms is a list of definitions of terms and concepts related to computer hardware, i.e. the physical and structural components of computers, architectural issues, and peripheral devices.

Computers can be classified, or typed, in many ways. Some common classifications of digital computers are given below. For others see Category:Classes of computers.

References

  1. 1 2 PC hardware : a beginner's guide. Osborne/McGraw-Hill. pp.  21. ISBN   9780072129908.
  2. "Parts of computer". Microsoft. Archived from the original on 27 November 2013. Retrieved 5 December 2013.
  3. von Neumann, John (1945). "First Draft of a Report on the EDVAC" (PDF). Archived from the original (PDF) on 9 August 2013. Retrieved 6 December 2013.Cite journal requires |journal= (help)
  4. Markgraf, Joey D. (2007). "The Von Neumann bottleneck". Archived from the original on 9 June 2011. Retrieved 24 August 2011.
  5. "Desktop computer vs. Laptop computer". www.computerhope.com. 30 December 2019. Retrieved 15 January 2020.
  6. Cipriani, Jason (29 May 2020). "Best 2-in-1 Detachable Laptops 2020: The Best Tablet-Laptop Hybrids". IGN. Retrieved 20 July 2020.
  7. "How long should a laptop battery last?". Computer Hope. Archived from the original on 21 December 2013. Retrieved 9 December 2013.
  8. 1 2 Harding, Scharon (17 September 2019). "What Is a MOSFET? A Basic Definition". Tom's Hardware . Retrieved 7 November 2019.
  9. "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.
  10. Domingo, Joel. "SSD vs. HDD: What's the Difference?". PCMag. Archived from the original on 19 March 2017. Retrieved 24 March 2017.
  11. Edwards, Benj (17 January 2012). "Evolution of the Solid-State Drive". PCWorld . Archived from the original on 25 March 2017. Retrieved 24 March 2017.
  12. PC hardware : a beginner's guide. Osborne/McGraw-Hill. 2001. pp.  20. ISBN   9780072129908.
  13. 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.
  14. 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.
  15. Estabrooks, Maurice (1995). Electronic technology, corporate strategy, and world transformation . Westport, Conn.: Quorum Books. p.  53. ISBN   0899309690.
  16. "Global revenue from computer hardware from 2005 to 2016". Statista. Retrieved 15 January 2020.
  17. "How to recycle your old computer". Digital Trends. 18 December 2016. Archived from the original on 17 April 2017. Retrieved 18 April 2017.
  18. Inc, Chris Keenan - Newtech Recycling. "Newtech Recycling Specializes in Computer Disposal, Laptop Disposal, Desktop Disposal Mainframe Disposal and Server Disposal". www.newtechrecycling.com. Archived from the original on 29 March 2017. Retrieved 18 April 2017.
  19. Robert-Tissot, Sarah (2011). "TANTALUM". Royal Australian Chemical instatute. Retrieved 3 March 2019.
  20. Padilla, Abraham (February 2019). "TANTALUM" (PDF). United states geological survey. Retrieved 3 March 2019.
  21. Bleiwas, D (July 2001). "Obsolete Computers, "Gold Mine," or High-Tech Trash? Resource Recovery from Recycling" (PDF). USGS. Retrieved 4 March 2019.
  22. LeBlanc, Rick. "Electronic Devices a Rich Source of Precious Metals for Recyclers". The Balance Small Business. Retrieved 4 March 2019.
  23. "The Toxic Components of Computers and Monitors". Archived from the original on 27 April 2017. Retrieved 26 April 2017.
  24. "What's Going On with Electronic Waste? – Electronics TakeBack Coalition". Archived from the original on 27 April 2017. Retrieved 26 April 2017.
  25. "Wire Recycling". All-Recycling-Facts.com. Archived from the original on 10 July 2017. Retrieved 5 May 2017.
  26. "Computer equipment recycling – Essential Guide". ComputerWeekly. Archived from the original on 21 December 2016. Retrieved 8 May 2017.
  27. Morgan, Russell (21 August 2006). "Tips and Tricks for Recycling Old Computers". SmartBiz. Retrieved 17 March 2009.
  28. Royte, Elizabeth (1 August 2005). "E-gad! Americans discard more than 100 million computers, cellphones and other electronic devices each year. As "e-waste" piles up, so does concern about this growing threat to the environment". Smithsonian Magazine . Smithsonian Institution . Retrieved 17 March 2009.
  29. Toothman, Jessika. "What Happens to your Discarded Old Computer?". HowStuffWorks.
  30. National Computer Recycling Act of 2005, H.R. 425, 109th Cong. (2005–2006)
  31. T. Gallo, Daniel (15 July 2013). "Broad Overview of E-Waste Management Policies in the U.S." (PDF). www.epa.gov. Retrieved 17 January 2020.
  32. 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.