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Output Devices: hardware that the computr uses to present data to the us

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Output Devices: hardware that the computr uses to present data to the us

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Screens: Are on all computer systems. CRT displays are the big, deep, monitors that used to be used in all desktop computers.
Speakers: as entertainment, in busy environments. Inemergecysituations where sound is more likely to be notices.
Printers: produce hard copies of documents and files. Inkjected printers work by squiring ink onto a page through a series of nozzles. The quality of the printer canbe measured bye DPI. Laser printers produce higher quality printouts than inkjetprinters but are also more expensive, specially color versions.
Hard disk security and privacy
The security of our data becomes increasingly important, especially when computers are lost or stolen, or old hardware is trown away.
- 117 drives (74%) contained data that they could recover and read.
-12 drives (9%) had been correctly erased.
-29 drives failed to work.
Where does data go when it was delated?
The MIT students were able to recover data from hard disks because deleting afile on a computer does not normally remove the file´s actual data. Deleating the file removes the pointer to the data from the hard disk´s File Allocation Table, which acts like an index to each file on the disk.
Solutions
There are only two ways to ensure data is fully removed from your hard disk: by either physically destroying the hard dik, or by using special disk wiping software. If the intention is to reuse the disk, a solution is to use specialist disk wiping or secure deletion software.
Storing Data: Bits and Bytes
Representing all of its data internally as binary digits-ones and zeroes. These ones and zeroes are known as bits.
Eight bits are grouped together, this is calleed bytes. Bytes themselves are grouped into increasingly larger units called kilobytes, megabytes, gigabytes and terabytes. A byte might represent a letter in a document, or it might represent the colour of a pixel on the screen.
ASCII
is a standard coding scheme for representing text using the English alphabet. Each byte of data represents a single character. ASCII uses one byte per character, the maximium number of characters ASCII can represent is 128.
Unicode
Uses  up to 4 bytes to represent each character, allowing many thousands of characters to be represented. Modern operating systems such as Windows Vista, Windows 7, Mac OS X, and Linux use Unicode.
Plain Text
ASCII and Unicode are both example of plain text standards. Plain text files are usually saved by programs known as  text editors.
Graphics Standards
Computer graphics are represented as bits and bytes just like all othr computers data. Each pixel in an image uses three bytes of storage space.
Failover systems
is one designed to keep a system running if the primary system fails, failover systems are usually redundant systems.
A RAID array is a failover system for hard disks.
An UPS provides a redundant power source in case of a mains electricity failure.
Ports and Conectors
Are used to connect input, output, storage and networking devices. Using standard ports allows hardware devices to be compatible with many different systems, saving on costs for both users and manufactures.
VGA
Used for connecting a satandard monitor to a computer or games controle. Projectors and interactive whiteboards alo use VGA connectios.
DVI
Are used to connector digital displays to digital video sources.
SATA and eSATA
Used for connectinng hard disks, DVD and Blue-ray players. eSATA is a version of SATA used for connecting external device.
IDE
An older standard for connecting hard disks. Used for devices like CD and DVD drives.
USB
For connecting a wide variety of peripherals including mice, keyboards, external hard disks, digital cameas, printers, scanners and flashdrives
FireWire
Used for different peripherals including digital video cameras and extrnal hard disks.
Ethernet
For wired Intrnet acces, available on virtually all computers.
PS2
For connecting mice and keyboards.

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Input Devices: are items of hardware thatallows entry of information into th computer

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Input Devices: are items of hardware thatallows entry of information into th computer

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Keyboards: QWERT keyboard is presented on all laptop and desktop computers. Multimedia keyboards are QWERTY keyoards with additional hotkeys for opening common applications. Used in conjunction with other keys to control features like the sound volume, screen brightness, or use of an external monitor or projector.

Concept Keyboards: each key is programmed to perform a custom function. Quick selection of choice. Used in restautants to enter the items acustomer has purchased. Each key can be programmed to represent a different item.

Soft Keyboards: is represented by a series of buttoms drawn on a monitor or scren. the user select options using a pointing device. Can be used in security conscious environments. Some banks used soft keyboards on the login pages of their online banking web sites to reduce the risk of key logging attacks.

Mice: a mouse is the standard pointing device on most desktop computers. Have two buttons a scroll wheel in the centre to perform tasks.

Trackballs: a large ball which is fixed in place so that the user can spin it around, controlling a pointer on the screen. Can make computers accessible to people who are unable to move a mouse across a desk

Touch Pads: are common in laptops, users can also use bars at the side to scrol text on the screen. Multi-touch touch pads allow more complex actions to be performed using severalfingers.

Touch Screens: allows users to interact with computers using their hand or a stylus. Used in airports and banks.

Microphones:allows sound data to be input into the computer. Are often used with video conferencing and Voice over IP software. This lets users talk betweentwocomputers over the internet.

Game controllers: Joysticks and game pads are two common input devices used by games players. They were used byNintendo´sWii games console.

Barcode Scanners: uses a laser to shine light onto a barcode label. The lines and the spacing between the lines on the barcode determine the amount of reflected light, interpreted as a number. Used in supermarkets. UPC defines how a barcode stores its information.

Magnetic Stripe Readers: store a small amount of data which is read using a magnetic stripe reader.

Smart cards: are plastic credit card that differ from normal magnetic stripe cards by having a higher storage capacity and an embedded processor. The processor controls access to the data stored on the card.

Optical Mark Recognition: for reading and countig multiple choice style answer papers. Uses reflected light to determine whether or not a mark existis in a box on a piece of paper, and then tallies the results.

Magnetic Ink Character Recognition: uses ink containing iron particles, making it magnetic. Text is writen in a special font, making it huma-readable.

Scanners: is a device for digitizing a piece of paper. The resolution of the scanner measured in DPI determines the quality of image produced. To convert a scanned image containing text back into normal text which can be edited in a word processing program.

Sensors and Probes: are used for measuring some aspect of the physical world Such data is analog data so its needs to be converted to digital data before it can be processed or stored by a computer.

Digital cameras: a useful way of inputting image, video, and sound into a computer. This can be done using a USB or FireWire connection.

Web Cams: is a low resolution video camera. Used to record the computer user, video conferencing.

Radio Tags: are used for locating objects. They emit radio signals which can be picked up and located by a receiver. Used to track wildlife.

Radio Frequency Identification: consists of two components: an WFID tag which is attached to the surface of an item and an RFID reader to query the tag and retrieve its information. Used in supermarkets.

Concerns about RFID: Each individual RFID is unique allows tracking of individal ites

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Hardware: the physical parts of the computer

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Hardware: the physical parts of the computer

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Types of computers

Supercomputers: are the largest, fastest, and more powerful computers. Achieve high processing through multiprocessing, separate processors working al together.

Mainframes: are very powerful computers. Are optimised for high data throughput, are able to read large amounts of data, process it and store the results very quickly.

Desktop computers: have ajustable monitors and separate keyboards and mice. HTPC are designed for multimedia entertaimet.

Laptop computers:feature a standard keyboard, an LD screen and a Wi-Fi card to allow acces to the internet.

Netbooks:are laptop computers designed for maximum portability. Provide acces to the internet and email in a portable way, very slow processor, a small amopunt of RAM, and a small screen.

Persona Digital Assistants: have a larger screen than mobile phones. Do not have a keyboard, the screen is used for touch input. Rapid communication.

Smart Phones: making voice calls and sending text messages. Have digital cameras, record video, sound and images. Run applications, have full keyboards and allow access to the world wide web and email.

Embedded systems: are found in cars, traffic lights, washing machines, digital watches, digital cameras and GPS. Programmed to perform only one type of specific task.