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A computer is a machine that follows programmed instructions to manipulate data. It takes in information or commands, processes them, may retain data or instructions, and presents results. A computer system usually includes the processor, memory, input and output devices, storage, and software working together.
What is a computer?
The Open University’s OpenLearn glossary defines a computer as “a machine that manipulates data following a list of instructions that have been programmed into it.” Put simply, a computer carries out instructions to work with data. It is not merely a device that accepts an input and produces an output: the programmed processing in between is central to what it does.
In introductory lessons, a computer is often described as a programmable electronic device that accepts input, processes it, and generates output. That is a useful starting point, but not every computer looks like a conventional PC or has the same visible parts. The term can refer to a processing device, while a computer system often means the device together with the hardware and software needed to use it.
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11The boundary is not identical in every context. For example, a U.S. FDA glossary reproduces an ANSI definition of a computer system that includes one or more computers, associated input/output peripherals and software, shared storage, and the execution of programs that manipulate data. In everyday use, the phrase may simply mean a computer and its connected components.
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How does a computer work?
A common way to explain a typical digital computer is the cycle of input, processing, storage, and output. These functions work together; storage can be shown as a step in the cycle or as a system component that supports the other steps.
- Input: A person types text, selects a command, taps a screen, or provides other data. Input devices translate what a person or another system provides into a form the computer can process.
- Processing: A program’s instructions are executed by the processor. The processor works with data represented in machine-readable form; it does not understand information in the human sense.
- Storage: Data and instructions may be held temporarily in memory or retained in storage for later use. What is kept, and for how long, depends on the program and the system.
- Output: The computer presents a result through a screen, speaker, printer, or another output device. Output devices convert results into forms people or other systems can use, such as images or sound.
For example, when you enter a sentence in a text editor, the keyboard supplies input. The program and processor handle the characters and commands, memory holds information while you work, and the screen displays the sentence. If you save the document, the system writes it to storage so it can be retrieved later.
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At a lower level, a CPU fetches instructions, decodes them, and executes them, working with data in registers or memory. OpenStax’s overview of computer systems explains this instruction-processing role alongside the functions of input and output devices.
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What are the main parts of a computer system?
A computer system’s exact components vary by purpose and design, but these roles are common:
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- Processor (CPU): Executes program instructions and performs operations on data.
- Memory: Holds data and instructions the processor needs while work is in progress.
- Storage: Retains data and programs for use beyond immediate processing.
- Input and output devices: Let the system receive data or commands and return results. A touchscreen, for example, can serve both roles.
- Software: Programs and instructions that tell the hardware what operations to perform.
These are functional roles, not a checklist of separate boxes that must be visible in every device. In a phone or an embedded controller, many components are integrated into a compact device.
What are the features of a computer?
Rather than treating “features” as a universal checklist, it is more accurate to describe capabilities that follow from the definition. Computers commonly execute programmed instructions, manipulate data, exchange input and output, and use memory or storage to hold data and instructions. Programmability also allows a general-purpose computer to perform different tasks when running different software.
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These capabilities vary in scope. A desktop can run many kinds of programs, while a controller inside an appliance may be programmed for a narrow task. Claims that all computers are always accurate or can solve every problem are too broad: results depend on the data supplied, the instructions and software, and the hardware.
What are the main types of computers?
There is no single complete taxonomy needed for everyday understanding. Grouping computers by form and purpose gives a useful picture of the range:
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| Type | Typical purpose | Portability and scope |
|---|---|---|
| Desktop and laptop PCs | General-purpose computing, commonly for individual use | Desktops are designed to stay in one place; laptops are portable. Both can run varied software. |
| Servers | Provide services or resources to other computers and systems | Typically serve multiple users or devices rather than one person’s direct, everyday computing. |
| Tablets and smartphones | Mobile personal computing, including communication and apps | Handheld and portable, with computing functions integrated into the device. |
| Embedded computers | Control or support a larger device or appliance | Usually built into the equipment they control and designed for a specific set of tasks. |
The examples are illustrative, not exhaustive. A washing machine or microwave oven, for instance, may use an embedded computer to control functions. These examples show why not every computer is a standalone device intended for general-purpose use.
How is a computer different from a computer system?
“Computer” can mean the machine or processing device itself. “Computer system” usually emphasizes the usable arrangement around it: processor, memory, input and output, storage, and software, sometimes including connected peripherals or shared resources. In casual conversation the terms may overlap, so context matters. A discussion of a CPU’s instruction execution is about a component; a discussion of a workstation with its programs and peripherals is more naturally about a system.
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