The Evolution: Computer Input and Output

There is a cycle that conveys inputs to processed data through the integration of input and output devices.

Input is the collection of unprocessed text, numbers, images, audio and video entered into the memory of a computer.  The input stage involves preparation of source document, data coding, data verification, data validation, data sorting and storage.

The source document which is the original source of data is prepared.  This includes vouchers, case notes, invoices or any document from which data originates.

During data coding and verification, data is encoded and verified to see if the unprocessed data meets the user’s requirement.  The data is transferred from the source document to the machine either manually or electronically.  It is a manual transfer if data is transcribed through a keyboard into a magnetic disk.  It is an electronic transfer if the hard disk source document is transmitted over a network.

At the data validation stage, data is validated with a computer controlled process.  User inputs are counter checked to see if it meets the input requirement of the user.  Inputs are checked to see if they are in line with the predefined format of the data to be processed.  If the user inputs a number instead of a text the computer rejects the input and gives the user an open option to correct the error.

At the sorting stage, the inputted data is sorted out into categories or classes. In the case of a database management environment, a primary key is used to sort records in the relevant master file.  This includes sorting data such as customer id, user name, batch number and address into the categories they belong.    

Data is then stored on the storage device of the computer for backup.  This is done so that data could be retrieved back in case of power failure or unintended manipulation.

The devices used for input operations include the keyboard, mouse, touchpad, joystick, light pen, touch screen, microphone, digital camera, point of sale terminals, automated teller machines and the biometric device which translates personal characteristics into a digital code.  It is used for user verification.

At the output stage, the processed data is displayed on the screen of a monitor as a soft copy.  It is then printed out on a printer as a hard copy.  The output stage also includes listening to processed sounds via a speaker.

Input / output generally refer to the communication between an information processing system and a user.  It is also the series of processes involves in converting data to information.

VDU’s AND KEYBAORDS

VDU means visual display unit of the computer this is the unit or output device that conveys text graphics and video information on a screen as a soft copy.  The visual display unit houses the display device of a computer.  The VDU could be the screen of a personal digital assistant, a phone or a laptop used to display the contents of a processed data.

The visual display unit associated with a computer is known as the monitor.  Three types of monitors are the Cathode ray tube, liquid crystal display monitor and the gas plasma monitor.

The cathode ray tube is a large sealed glass tube which has a screen in front of it.  Tiny dots of phosphor material coat the screen on a cathode ray tube.  The dot consist of a green, red and blue phosphor which combine together to make up a pixel.  Electronic beam moves back and forth across the back of the screen causing the dots on the front of the screen to glow.  This produces an image on the screen.  An energy star program was developed by the United States department of energy as well as the United States environmental protection agency to reduce electricity consumption.

It involves some stages for processed data to be displayed on the cathode ray tube monitor.  The processor sends digital video to the video card.  The video cards digital video to analog converter converts the digital video data to an analog signal.  The analog signal is sent through a cable to the cathode ray tube monitor.  The monitor separates the analog signal into red, green and blue signals.  Electron guns fire the three colour signals to the front of the cathode ray tube.  The image of the processed data is then displayed on the screen when the electrons hit phosphor dots on the back of the screen.

The cathode ray tubes are the oldest types of monitors and are being gradually faced off in the 21^st century since the inception of the liquid crystal display monitors.

The liquid crystal display monitor is a desktop monitor that uses a liquid crystal display to produce images.  It is also called the liquid crystal display flat monitor panel.  The LCD produces sharp and flicker-free images unlike the cathode ray tube monitors.  It uses less than one third the power consumed by a CRT monitor and produces less heat.  It does not produce electromagnetic radiation.  These monitors have made work easier for mass communication and crime investigation users.  It also meets requirements of gamers.

It allows a side by side attachment to produce different views of a document on the screen.  Video editors, network administrators, web developers, graphic designers, engineers and architects have greatly benefited from this feature.  The internal components include liquid crystal cells, transparent electrodes, alignment layer, colour filter, polarizing glass filter and fluorescent tube panel.  For processed data to be displayed on an LCD, a panel of fluorescent tubes emit light waves through polarizing glass filter, which guides the light toward the layer of liquid crystal cells.

As light passes through the liquid crystal, an electrical charge from a transistor cause some of the cells to twist making the light waves to bend as they pass through a colour filter when the light reaches the second polarizing glass filter, light is allowed to pass through any cells that line up at the same angle as the twist polarizing glass filter.  The absence and presence of coloured light then cause an image to appear on the display.

The Gas plasma monitor uses gas plasma technology.  The layer that holds liquid on an LCD is substituted with gas.  When voltage is applied the gas releases ultraviolet light which causes the pixels on the screen to glow and produce an image of a processed data.

Gas plasma monitors offer higher picture quality and larger screen sizes than the LCD.

KEYBOARD

The keyboard is an input device that allows a user to enter alpha numeric data into the computer for processing.  This input device contains keys a user press to enter data into a computer.  The keyboard is made up of function keys, window keys, wrist rest, application keys, arrow keys, numeric keypad, internet control keys, CD and DVD controls.

A computer keyboard has from 101 to 105 keys.  It contains keys that allow a user to position a cursor.  The keyboard is a primary input device.  It is a very important one because it gives users such as web developers and database administrators, a wide range of options during data input.

It is connected to a computers’ serial port through cable while some keyboards are wireless.  A wireless keyboard uses batteries and transmits data with blue tooth, radio waves and infrared waves.  Most computers come with installed drivers for keyboards so they do not need installation to be configured and used.

ENCODING TO DISK OR TAPE

The information stored on the disk or tape is digital information which is a stream of ones and zeros.  Data needs to be converted to magnetic information for it to be stored on the disk or tape.  This is done by an integrated controller built into the hard drive.  This combines with the sense and amplification circuits to perform the encoding.  These circuits are used to interpret the weak signals read from the platters themselves.

The magnetic information on the disk consists of a stream of magnetic fields.  The magnet has both north and south poles, and the magnetic energy called the flux flows from the North Pole to the South Pole.  Information is stored on the hard disk by encoding information into a series of magnetic fields.  This is done by placing the magnetic fields in one of the two polarities.  This occurs so that the North Pole arrives before the South Pole as the disk spins or so that the South Pole arrives before the North Pole as it spins.

It is conceptually simple to match O and I digital information to “N-S and S-N” magnetic fields.  Methods of data recording on magnetic tapes includes return to zero, bipolar return to zero, carrier suppressed return to zero, return to bias, non return to zero, non return to zero inverting, phase encoding, bipolar  mark, differential Manchester and modified frequency modulation.

Return to zero (RZ) involves a one represented by a pulse of magnetization in one direction and zero is represented by no magnetization. 

Bipolar return to zero (RZ(B)) has to do with one bits recorded as pulses of magnetization in one direction, and zero bits as pulses of magnetization in the other direction.

Carrier Suppressed Return to Zero (CSRZ) is a modulation where pulses represent ones, and the absence of a pulse represents zero, but successive pulses alternate in direction.

Return to Bias (RB) involves recording of pulses in one direction for a one bit, but no pulse is recorded for zero.

Non Return to Zero (NRS) involves recording of a signal one way for one and the opposite way for zero without space between bits.

Non Return to Zero Inventing (NRZI) involves the indication of a one when there is a transition from one direction of magnetization to the other no change indicates a zero. 

Phase Encoding (PE) is also known as Biphase level or Manchester II + 180^o.  This method was implemented when the density of reel to reel computer tapes were increased to 1600 bpi.

Biphase Mark (BM) also called Manchester code and frequency modulation.  This variant of phase encoding has a transition at way boundary between bit times, but indicates a one by a polarity transition within the bit and a zero by no transition within the bit.

Differential Manchester (DM) involves a transition within each bit and alternates the direction of this transition when the bits stay the same and keeps the direction of transitions constant when bits differ.

Modified Frequency Modulation (MFM) also called Miller code.  This combines the low band width requirement of NRZI with the self clocking characteristic of PE.

DOCUMENT READING CARD

This is also called a card reader.  It is a device that reads and writes data, instructions and information stored on PC cards or memory cards.

Paper or cardboard punch cards were used in the early computer age before the inception of modern card readers.

Modern card readers are electronic devices that use plastic cards imprinted with bar codes, magnetic strips and computer chips to read documents.  The document reading card is an input device.

READING DEVICES

A reading device is the hardware a user uses to read an e book or a processed document.  These include a rocket e book device, web pad, go reader and multipurpose palm top.

REB1100 and REB1200 are reading devices developed by Gemstar TV guide international subsidiaries Navomedia (Rocket ebook developer) and soft press.  The rocket eBook is the most popular dedicated eBook reading device.

PRINTED OUT

Printed out is also called a hard copy.  It is a printed copy of processed data from a computer.  It is a material a user can read directly.  The same information viewed on the screen of a computer monitor as a softcopy is sent to the printer which is an output device and printed out as a print out or hard copy.  A print out is a permanent reproduction.  It is printed on objects such as papers and photo cards.  Examples are pictures, email messages and account balances.

COMPUTER OUTPUT ON MICROFORM

Microforms are such as films or paper containing micro-reproduction of documents for transmission, storage, reading and printing.  A microform image may be provided as positive or negative.

The three formats are microfilm, microfiche and micro cards.

The microfilm stores microscopic images of documents on 100 to 215 foot roll of film.  It is also called reels.

The microfiche stores images of documents on a small sheet of film usually about 4 inches by 6 inches.  It is also called flat sheet.

The micro card is a format similar to the micro fliche but it’s no longer produced.  The microforms are displayed through computer output devices such as, display screens, printers, plotters and synthesizers.  The processed data can be viewed on display screens such as LCD monitors, CRT monitor, gas plasma monitors and projectors.

Printers such as laser and bubble jet printers could be used to print out the processed data.  Plotters used for printing out vector graphics can also be used.  A synthesizer can be used in the case of an audio data.