The Components of a Computer

A computer contains many electric, electronic, and mechanical components known as hardware. These components include input devices, output devices, a system unit, storage devices, and communications devices.

1. Input Devices

An input device is any hardware component that allows you to enter data and instructions
into a computer. Five widely used input devices are the keyboard, mouse, microphone, scanner, and Web cam.


A computer keyboard contains keys you press to enter data into the computer. For security
purposes, some keyboards include a fingerprint reader, which allows you to work with the computer only if your fingerprint is recognized.


A mouse is a small handheld device. With the mouse, you control movement of a small symbol on the screen, called the pointer, and you make selections from the screen.
A microphone allows you to speak into the computer. A scanner converts printed material
(such as text and pictures) into a form the computer can use.


A Web cam is a digital video camera that allows you to create movies or take pictures
and store them on the computer instead of on tape or film.

2. Output Devices

An output device is any hardware component that conveys information to one or more people. Three commonly used output devices are a printer, a monitor, and speakers.


A printer produces text and graphics on a physical medium such as paper. A monitor
displays text, graphics, and videos on a screen. Speakers allow you to hear music, voice, and other audio (sounds).

3. System Unit

The system unit is a case that contains the electronic components of the computer
that are used to process data. The circuitry of the system unit usually is part
of or is connected to a circuit board called the motherboard.


Two main components on the motherboard are the processor and memory. The processor,
also called a CPU (central processing unit), is the electronic component that interprets and carries out the basic instructions that operate the computer. Memory consists of electronic components that store instructions waiting to be executed and data needed by those instructions.


Although some forms of memory are permanent, most memory keeps data and
instructions temporarily, which means its contents are erased when the computer is
shut off.

4. Storage Devices

Storage holds data, instructions, and information for future use. For example, computers
can store hundreds or millions of customer names and addresses. Storage holds these
items permanently.


A computer keeps data, instructions, and information on storage media . Examples of storage media are USB flash drives, hard disks, optical discs, and memory cards. A storage device records (writes) and/or retrieves (reads) items to and from
storage media. Drives and readers/writers, which are types of storage devices, accept a specific kind of storage media. For example, a DVD drive (storage device) accepts a DVD (storage media). Storage devices often function as a source of input because they
transfer items from storage to memory.


A USB flash drive is a portable storage device that is small and lightweight enough to
be transported on a keychain or in a pocket. The average USB flash drive can hold about 4 billion characters. You plug a USB flash drive in a special, easily accessible opening
on the computer.


A hard disk provides much greater storage capacity than a USB flash drive. The average
hard disk can hold more than 320 billion characters. Hard disks are enclosed in an airtight, sealed case. Although some are portable, most are housed inside the system unit.


Portable hard disks are either external or removable. An external hard disk is a separate, freestanding unit, whereas you insert and remove a removable hard disk from the computer or a device connected to the computer.


An optical disc is a flat, round, portable metal disc with a plastic coating. CDs, DVDs,
and Blu-ray Discs are three types of optical discs. A CD can hold from 650 mil lion to
1 billion characters. Some DVDs can store two full-length movies or 17 billion characters. Blu-ray Discs can store about 46 hours of standard video, or 100 billion
characters.


Some mobile devices, such as digital cameras, use memory cards as the storage media. You can use a card reader/writer to transfer the stored items, such as digital photos, from
the memory card to a computer or printer.

5. Communications Devices

A communications device is a hardware component that enables a computer to send
(transmit) and receive data, instructions, and information to and from one or more computers or mobile devices. A widely used communications device is a modem.


Communications occur over cables, telephone lines, cellular radio networks, satellites, and other transmission media. Some transmission media, such as satellites and cellular radio networks, are wireless, which means they have no physical lines or wires.