Hardware

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Input devices

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There are many input formats which enable us to gather up and collect information, and enter data and instructions into the computer. Input devices can be manual or automatic.

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Concept Keyboard

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This is a flat board that contains a grid of buttons. Each button can be programmed to follow instructions. An overlay sheet is placed on the grid with an explanation for each button. They are used in primary schools with young children. Many modern fast food restaurants have overlays with either a description or picture of the meals that are available to make ordering easier.

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Digital cameras

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Take pictures and store them as a digital photographic image that can be read by a computer. You can then transfer the images directly from your camera on to your computer.

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Microphones

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They're used to input sound information and can be used with a voice recognition system which processes the information. This can be used with a word processing program to enter text. It can also be used as part of security systems - only certain digitally stored voices will gain access.

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Touch screen

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A special type of VDU, which has a grid of light beams or fine wires criss-crossing the screen. When the screen is touched (usually to choose an on-screen option), the computer senses where you have pressed. The information is stored on the computer and the touch screen is simply an interface. Touch screens have the benefit of being very robust and easy to operate and reprogram, hence why they are used in public places.

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Video digitiser

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Takes an image from a video camera or television and converts it so that it can be used by, and stored on, a computer. Video sequences captured using a video digitiser are often used in multimedia presentations.

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Graphics tablets

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Consist of a flat pad (the tablet) on which the user draws with a special pen. As the user draws on the pad the image is created on the screen. Using a graphics tablet a designer can produce very accurate on-screen drawings.

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Scanners

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A cheap and common way of getting images into a computer. They can also be used with OCR (Optical Character Recognition) software to scan in text.

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Other manual input devices

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Mouse
Tracker ball
Joystick
Light pen

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Automatic input devices

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Sensors
Barcode reader

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Barcodes

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Different groups of vertical bars that can be read by a barcode reader. Barcodes are printed on nearly every product that you can buy. Shops use barcodes because they enable the shops to maintain their stock control system. The barcode contains the product details such as product name, size, manufacturer, country of origin. The price is looked up from the shop's database. When the bar code is scanned, the shop's stock is automatically reduced by one.

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MICR (Magnetic Ink Character Reader)

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Magnetic ink characters are the strange looking numbers that appear at the bottom of cheques. Banks use MICR to read the numbers from the bottom of cheques to obtain data such as account numbers and bank sort codes. This particular font is used because it is easy for a machine to discriminate between characters. The ink is magnetised because it makes it immune to creases or dirty marks.

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Magnetic strip (or stripe) reader

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Magnetic stripes are built into many plastic cards such as cheque guarantee cards, cash-point cards and personal identity cards. The magnetic strip on the back of the card can hold the personal details of the card owner and, with the necessary PIN, will allow access to secure information e.g. bank account details. Data stored on the strip is scanned and input into a computer system by a magnetic stripe reader.

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OMR (Optical Mark Reader)

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This reads marks made by pencil on a printed form into the computer. OMR systems are suited to reading pre-printed forms and check-boxes such as National Lottery number selection sheets and multiple-choice exam papers.

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Output formats

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printed-paper
saved disk file
sound
video
on-screen documents

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Output Devices

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They are all of those things that let your computer 'talk' back to you and present information.

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Monitors (Visual Display Units - VDUs)

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Desktop monitors which are also known as Cathode Ray Tube (CRT)

Liquid Crystal Displays (LCD) which are also known as Thin Film Transistors (TFT)

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Printers

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Laser printers produce a very high quality output, are very quiet and very fast. Laser colour printers are quite expensive to buy.

Ink-jet printers offer black and white or colour printing with reduced levels of quality and speed. Colour ink jet printers are cheaper to buy than colour laser printers.

Dot-matrix printers are not so common today. They are comparatively noisy and low quality but are cheap to run and are used when carbon copies or duplicates need to be made, such as for wage slips. Also, they are useful in dirty environments such as a garage because they are much sturdier than the other two types of printer.

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Plotters

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A plotter can be used to produce high quality, accurate, A3 size or bigger drawings. They are usually used for Computer Aided Design (CAD) and Computer Aided Manufacture (CAM) applications such as printing out plans for houses or car parts.

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Other output devices

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Speakers
LCD projectors

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Output can also be in the form of...

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...instructions to a device such as a robot arm.

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Barcode

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A group of vertical bars that can be read by an barcode scanner. The price is held on the database and the barcode is the primary key that is used to access the price.

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Scanner

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A device that can read text or pictures printed on paper and translate the information into a form the computer can use.

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VDU

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Visual Display Unit - a monitor.

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ROM

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Read Only Memory - a type of permanent memory where the content cannot be changed by a program or user.

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RAM

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Random Access Memory - a fast temporary type of memory in which programs and data are stored whilst the computer is switched on.

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Hard disk

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Magnetic disks which are used as a backing storage system and are fixed inside a computer. A hard disk can store; the operating system, software applications or programmes, the majority of your data files.

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Floppy disks

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3.5-inch portable magnetic disks, which are used as a backing storage system.

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Floppy disks have three main uses...

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to transfer small files of data from one machine to another

to back up important small files that are stored on your hard disk

to store restricted files that you don't want all other users of your computer seeing

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Zip disks...

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are like large floppy disks, but can store 250 megabytes or more of data. They need their own drive. As with floppy disks, they are not used as frequently now as zip disk technology has been superseded.

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External backing stores: optical disks

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There are several different types of optical disk, although they all look pretty much the same.

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CD-ROM

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Compact Disk Read Only Memory. These disks are optical disks that use the same technology as musical compact disks. They store up to 700Mb of data and a laser beam is used to read the data off the disk.

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CD-R and CD-RW

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CD-Rs are blank optical disks onto which you can write data with a piece of hardware called a CD writer. They have a similar capacity to CD-ROMs and can be set up as multi-session disks and so you can write to them many times. Eventually of course, you will run out of disk space as you never go over the same area twice.

CD-RWs are blank optical disks which can be written and re-written to.
They can hold a lot more data & multimedia material.

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DVD

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DVD stands for Digital Versatile Disk. There are several formats on the market, the more expensive ones being recordable like CDs. They are the same size as CDs, but hold much more data - a single sided, single layer disc can hold up to 4.7 gigabytes with a dual layer disc holding 8.4 gigabytes. Now DVDs are commonly used for video recordings, so you will often see them measured in minutes e.g. 4.7Gb = 120 minutes.

DVD drives are often found on computers as combined DVD and CD-RW drives, so the computer can read and show DVD films, as well as read and write CDs.
They can hold a lot more data & multimedia material.

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External backing stores: magnetic tape

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Magnetic tapes or cartridges are principally used for backup of important files from the hard disk drive and the long term storage and archiving of data.

Advantages
They are small, robust, portable and as they provide low cost storage per Gigabyte, they are often used to back up important documents and files from the hard disk drive.

Disadvantages
They are very slow to find data or files and provide serial access which means that all the data on the tape before the part you need must be read before you can access the required data.

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External hard drives

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These can store very large amounts of data - up to a terabyte - and can be plugged in to your computer via a USB or Firewire port to provide extra storage.
They hold large quantities of data, and are portable.

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Memory sticks

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A memory stick is a small 'pen top' sized device that holds a large amount of memory - from 512Mb to 1Gb upwards depending on the price paid. This is a USB device and can be used in a similar way to a floppy disk, but is inserted into the USB port - it is then seen by the computer as a removable drive.
They hold large quantities of data, and are portable.