THE COMPONENTS OF A COMPUTERS

A computer contains many electric, electronic, and mechanical components know as hardware. These components include input devices, output devices, a system unit, storage devices, and communications devices.
INPUT DEVICES
An input device is any hardware component that allows you enter data and instructions into a computer. Six widely used input devices are the keyboard, mouse, microphone, scanner, digital camera, and web cam.
A computer keyboard contains keys you press to enter data into the computers. For security purposes, some keyboards have a built in fingerprint reader, which allows you to work with the computer only if your fingerprint is recognized.
A mouse is small handheld device. With the mouse, you control movement of 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 convert printed material (such as text and pictures) into a form the computer can use.
With a digital camera, you take pictures and then transfer them to the computer or printer instead of storing the images on traditional film. A web cam is digital video camera that allows you to create movies or take still pictures electronically.
OUTPUT DEVICES
An output device is any hardware component that conveys information to one o more people. Four commonly used output devices are a printer, a monitor, speakers, and a portable media player.
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 (sound). You can transfer audio, video, and digital images from a computer to a potable media player and then listen to the audio, watch the video, or view the images on the media player.
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 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 instruction temporarily, which means its contents are erased when the computer is shut off.
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, CDs, DVDs, 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 pocket. The average USB flash drive can hold about 2 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, free standing unit, whereas you insert and remove a removable hard disk from the computer or a device connected to the computer.
A compact disc is flat, round, portable metal disc with a plastic coating. One type of compact disc is a CD, which can hold from 650 million to 1 billion characters. You can access a CD using most CD and DVD drives. Another type of compact disc is a DVD, some of which have enough storage capacity to store two full length movies or 17 billion characters. To access a DVD, you need a DVD drive.
Some portable devices, such as digital cameras, use memory cards as the storage media. You then can transfer the stored items, such as digital photos, from the memory card to a computer or printer using a card reader/writer.
COMMUNICATIONS DEVICES
A communications devices is a hardware component that enables a computer to send (transmit) and receive data, instructions, and information to and from one or more computers. A widely used communications device is a modem.
Communications occur over cables, telephones 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.