A computer is a programmable device that stores, retrieves, and processes data. The term "computer" was originally given to humans (human computers) who performed numerical calculations using mechanical calculators, such as the abacus and slide rule. The term was later given to mechanical devices as they began replacing human computers. Today's computers are electronic devices that accept data (input), process that data, produce output, and store (storage) the results (IPOS).
Below is a picture of a computer with each of the main components. You can see the desktop computer, flat-panel display, speakers, keyboard, and mouse in the picture below. We've also labeled each of the input devices and output devices.
History of the computer
The first digital computer and what most people think of as a computer was called the ENIAC (Electronic Numerical Integrator and Computer). It was built during World War II (1943-1946) and was designed to help automate the calculations being done by human computers. By doing these calculations on a computer, they could achieve results much faster and with fewer errors.
Early computers like the ENIAC used vacuum tubes and were large (sometimes room size) and only found in businesses, universities, or governments. Later, computers began utilizing transistors and smaller and cheaper parts that allowed the ordinary person to own a computer.
How are computers used today?
Today, computers do jobs that used to be complicated much simpler. For example, you can write a letter in a word processor, edit it anytime, spell check, print copies, and send it to someone across the world in seconds. All these activities would have taken someone days, if not months, to do before. Also, these examples are a small fraction of what computers can do.
What components make up a desktop computer?
Today's desktop computers have some or all the components (hardware) and peripherals below. As technology advances, older technologies, such as a floppy disk drive and Zip drive (shown below), are no longer required or included.
- Case or Chassis
- Case Fan
- Optical drive: Blu-ray, CD-ROM, CD-R, CD-RW, or DVD.
- CPU (central processing unit)
- Floppy disk drive
- Hard drive
- RAM (random-access memory)
- Monitor, LCD (liquid-crystal display), or another display device.
- Network card
- Power Supply
- Sound card
- Video card
What parts are needed for a computer to work?
A computer does not require all the components mentioned above. However, a computer cannot function without having at the very minimum the parts listed below.
- Processor - Component that executes instructions from the software and hardware.
- Memory - Temporary primary storage for data traveling between the storage and CPU.
- Motherboard (with onboard video) - Component that connects all components.
- Storage device (e.g., hard drive) - Slower secondary storage that permanently stores data.
However, if you had a computer with only the minimum parts above, you would be unable to communicate with it until you connected at least one input device (e.g., keyboard). Also, you would need at least one output device (e.g., monitor) for you to see what is happening.
Once a computer is set up, running, and connected to a network, you could disconnect the keyboard and monitor and remotely connect. Most servers and computers in data centers are used and controlled remotely.
All computers have different types of connections. An example of the back of a personal computer and brief descriptions of each connection is found on our computer connections page.
Types of computers
Computers can be classified as one of three types of computers: a general-purpose computer, special-purpose computer, or specialized computer.
A general-purpose computer is what most people think of when thinking about a computer and is what this page covers.
A special-purpose computer is embedded in almost all electronic devices and is the most widely-used computer. This computer is designed for a specific task and is found in ATMs, cars, microwaves, TVs, the VCR (video cassette recorder), and other home electronics. See our special-purpose computer page for further information and examples.
A specialized computer is like a general-purpose computer but is designed only to perform one or a few different tasks. See our specialized computer for further information and examples of these computers.
When talking about a computer or a "PC," you're usually referring to a desktop computer found in a home or office. However, the lines of what makes these computers are blurring. Below are different examples of what's considered a computer today.
The picture above shows several types of computers and computing devices and is an example of their differences. Below is a complete list of general-purpose computers of past and present.
Some computers could use many different classifications. For example, a desktop computer could also be classified as a gaming computer and a personal computer.
- Custom-built PC
- Desktop computer
- Diskless workstation and Thin client
- Gaming computer
- Hybrid computer
- Laptop, portable, notebook computer
- PDA (personal digital assistant)
- Personal computer
- Prebuilt computer
- Quantum computer
- Stick computer
Who makes computers?
Today, there are two types of computers: the PC (IBM compatible) and Apple Mac. Many companies make and build PCs, and if you get all the necessary parts for a computer, you can even build a custom PC. However, with Apple computers, only Apple designs and makes these computers. See our computer companies page for a listing of companies (OEMs) that make and build computers.