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The central processing unit fetches and executes program instructions and performs the arithmetic and logic operations. The other parts either store data or deliver electricity to the system.
An input device sends data into the computer; the key presses on a keyboard are converted into signals the computer can process. Monitors, printers and speakers only present results produced by the computer.
A printer transfers the document onto paper, producing what is called a hard copy. A scanner, microphone and webcam all capture information from the outside world instead.
RAM is volatile, meaning it needs electrical power to keep its contents, so everything in it disappears at shutdown. Saving work to storage is a separate action performed by the user or by the software.
An operating system manages the hardware and provides services that other programs rely on, and Android is a mobile operating system. Excel, Firefox and Photoshop are application programs that run on top of an operating system.
Storage units increase in the order byte, kilobyte, megabyte, gigabyte, terabyte, each step being roughly one thousand times larger. A terabyte therefore holds far more data than a gigabyte.
An SSD stores data in flash memory chips, so nothing physically moves inside it and it resists shock and vibration better. A hard disk relies on spinning platters and a moving read/write head.
USB is a standard connection for peripherals such as mice, keyboards, printers and flash drives, and it can also deliver power to them. Mains power, telephone connections and cooling are handled by entirely different components.
Application software lets the user carry out a task such as writing a document or building a spreadsheet. Windows is an operating system, a driver lets the operating system control a device, and the BIOS is firmware.
The screen displays information, which is output, and it also senses finger touches so the user can give commands, which is input. It therefore performs both roles at once.
Cloud storage keeps files on remote servers run by a provider and reaches them through an internet connection. A local copy exists only if the service also synchronises or downloads the files.
Compression reduces the number of bits needed to represent the data, so the file occupies less space and travels faster over a network. It is not a security or antivirus measure.
Firmware is held on a chip on the motherboard and runs first at start-up, performing a power-on self-test and locating the bootable device that holds the operating system. It is not the graphical interface of the operating system and does not hold user files.
The motherboard is the main circuit board of the computer, and the processor, memory and expansion cards are fitted to it and exchange data through its circuitry. The other items supply power, show output or store files.
Resolution states how many horizontal and vertical picture elements the display can show, so 1920 × 1080 means 1920 pixels across and 1080 down. Physical size, colour depth and refresh rate are separate specifications.
The backlight and heat both drain a battery quickly, so lowering brightness and keeping the machine cool extends run time. Closing unused programs also reduces the load on the processor.
A dot matrix printer strikes an inked ribbon against the paper, and this impact transfers print through to carbon-backed sheets underneath. Inkjet, laser and thermal printers do not use impact and so cannot produce carbon copies.
Video editing involves huge numbers of similar calculations on image frames, which a GPU performs in parallel far faster than a general-purpose CPU. The other tasks place almost no demand on the graphics processor.
Old computers contain metals, plastics and hazardous substances that must be recovered or treated safely, which is exactly what certified recyclers do. Binning or burning them pollutes the environment, and storing them does not deal with the problem.
Good ergonomic posture keeps the back supported, the feet flat and the top of the screen close to eye level, which reduces strain on the neck, shoulders and wrists. The other positions increase muscular and joint stress over time.
HDMI carries digital video and sound together over a single cable, typically from a computer to a monitor, projector or television. Network, charging and printer connections use other types of port.
RAM gives the processor fast, temporary workspace for the programs and documents that are currently open. Its contents are cleared when the machine is switched off, so it is not a permanent store.
A scanner shines light onto the page and records the reflected pattern as digital image data that can be stored on the computer. Plotters, speakers and projectors produce output rather than capture it.
ROM is non-volatile: it keeps its contents without power and is written at manufacture or with special tools, and it commonly holds start-up instructions such as firmware. It is RAM, not ROM, that provides the volatile working memory used by running programs.
When RAM is exhausted, the operating system moves data to much slower disk storage, and this constant swapping makes the machine feel sluggish. Adding more memory or closing programs relieves the problem.
An output device presents processed data from the computer to the user, and a monitor does this by displaying images and text on a screen. Input devices such as a mouse, a scanner and a keyboard send data into the computer instead.
A byte is defined as a group of eight binary digits, so one byte equals eight bits. Storage capacities are normally quoted in bytes and their multiples, such as kilobytes and megabytes.
The processor, or CPU, fetches instructions from memory, decodes them and executes them. Other components either store data, supply electricity or present results to the user.
An operating system controls hardware resources, manages files and memory, and provides services that applications rely on. Browsers, spreadsheets and word processors are applications that run on top of it.
A pointing device lets the user move a pointer on screen and select items, and a mouse does this by detecting movement across a surface. Monitors, printers and speakers deliver output rather than accept pointing input.
A USB flash drive contains flash memory chips and has a built-in connector that fits a USB port, so it needs no separate reader. It is small, portable and has no moving parts.
A peripheral is any device attached to and controlled by a computer to add functionality, such as a printer, scanner or webcam. The other terms refer to software or to instructions built into hardware.
Android is designed for smartphones and tablets, with touch input and app stores as central features. The other systems listed are built for desktop, laptop or server computers.
Cache memory sits on or very close to the processor and holds frequently used data, making it faster than main memory. Storage media such as hard disks and optical discs are much slower than either.
A touchpad senses finger movement and translates it into pointer movement on screen, and taps or clicks act as button presses. It replaces an external mouse when one is not available.
A hard disk drive spins rigid platters coated with magnetic material and uses read/write heads to store and retrieve data. The other devices listed store data in flash memory chips and have no moving parts.
Blu-ray uses a blue laser with a shorter wavelength, which allows data to be packed more densely, so a single-layer disc holds about 25 GB. DVDs hold about 4.7 GB and CDs about 700 MB.
Dpi stands for dots per inch and measures how many ink or toner dots the printer can place in one inch, which affects the sharpness of the printed image. Pages per minute measures speed instead.
A laser printer uses a laser to draw the page image on a drum, which attracts charged toner powder that is then fused onto the paper with heat. Inkjet printers spray liquid ink instead.
Bluetooth is a short-range radio technology designed for linking peripherals such as mice, keyboards and headsets to a computer. Ethernet and HDMI are wired connections, and USB is a cable standard.
A UPS contains a battery that keeps a computer running for a short time when mains power fails, allowing work to be saved and the system to shut down safely. It also helps smooth out power surges and dips.
A multifunction printer combines several document devices in one unit, most commonly printing, scanning and photocopying, and often faxing. Browsing, editing and cooling are not printer functions.
Each step up the storage scale is about one thousand times larger, so one gigabyte is roughly one thousand megabytes. This relationship applies to kilobytes, megabytes, gigabytes and terabytes.
Sleep mode powers down the display and most components while keeping the current session in memory, so the computer uses much less electricity until it is woken. High performance mode does the opposite by keeping components running at full power.
With plug and play, the operating system detects a newly connected device and loads a suitable driver without manual configuration. This allows peripherals such as mice and USB drives to work as soon as they are attached.
The clock speed states how many cycles the processor performs each second, and one gigahertz equals one billion cycles per second. It is only one indicator of performance, because the work done per cycle also matters.
A 64-bit system works with larger memory addresses, so it can refer to a far greater number of memory locations than a 32-bit system, which is limited to about 4 GB. File compression and use of disk space are separate features and do not raise that limit.
A driver is system software because it lets the operating system communicate with a specific piece of hardware. Application software performs tasks for the user, while firmware is built into the device itself.
When RAM is full, the operating system can move less active data to a reserved area of storage called virtual memory, freeing RAM for current work. Accessing that area is slower, so heavy use of virtual memory reduces performance.
Each core can work on instructions independently, so a multi-core processor can handle several tasks or threads in parallel and stays responsive under heavy workloads. It still needs memory and storage, and it does not change display output.