LECTURE THREE COMPUTER HARDWARE
Introduction • Computer hardware is the name given to all the physical devices found in a computer system.
They correspond to ears, eyes, mouth, hands, brain, mouth, books and so on. in the human processing system. Figure 3.1 is an illustration of the basic elements of a computer system or the hardware.
Input Units • These units read data, data files and programs into the computer. There are several types of input facilities that differ in terms of the entries they accept.
The selection of the facilities is influenced by the class of computers installed, and the associated processing requirements. Most input facilities are combined with output facilities and hence referred to as I/O (Input/Output) units.
Functions of Input Units • Accept data from the user into the Computer System. • Accept instructions from the users. • Accept commands for running or aborting or halting a program from the user.
Could be either on-line data inputting or off-line data inputting. • Types of Input Devices • Keyboard Devices • Pointing Devices • Pen-based computing
Voice Recognition • Scanners • Magnetic Devices • Intermediate input devices • The major trend for input technologies has been towards a more natural user interface for computer users e.g. pointing devices, touch pads, voice recognition etc.
Keyboard devices are used for entries and are connected to several different devices as following: • Visual Display Unit (VDU): It has a keyboard for data and instruction input.
The keyboard is similar to that of a normal typewriter with except that the VDU keyboard has got extra keys for controlling and editing the inputs. It has a screen which displays information in a page of rows and columns.
Terminals: Terminals can be described as input/output devices with communication capabilities and they may have limited processing power. A terminal is described as “INTELLIGENT” if it has some processing power. Those without are called “DUMMY”
c) Point-of-sale terminals: Point-of-sale terminals are essentially electronic cash registers that are linked to a computer, or record data onto storage devices. In their simplest form, they may simply transmit the details of a transaction to the computer for processing.
The more complex terminals can communicate for such purposes as checking the credit of a customer, obtaining prices from file and ascertaining availability of stock. If a customer’s bank or credit account is debited, this is Electronic Fund Transfer at Point of Sale (EFTPOS).
The terminal usually includes a keyboard for manual entry of data. A bar-code reader may also be provided, typically to read stock codes. • d) Console: A console is a device used by the computer operators to communicate with users.
Keyboard devices are widely used. • They have the keyboard for typing in data and/or instructions that go in a format the computer can understand • Issuing commands. • Making choices. • Responding to prompts displayed on the screen.
Examples of pointing devices that work with the keyboard are: • Electronic Mouse: This is most popular pointing device used to move cursor on the screen, as well as issue commands and make menu and icon selections.
Track Ball: A stationary device related to the mouse. It consists of a roller ball mounted on the computer. One turns a roller ball to move the cursor on the screen.
Pointing Stick (track point): This device is found on the keyboard, one presses it to direct the cursor. The cursor moves in the direction of the pressure one place on the stick.
The touch pad: A small rectangular touch – sensitive surface, usually placed below the keyboard. The cursor moves in the direction your finger moves on the pad.
Touch Screen: A touch sensitive screen where when one touches the icon on the screen, a command is executed against the icon.
Handwriting – recognition systems convert script into text quickly. These computers have fast processors and software that recognizes hand written or typed information. Hand drawing pen-like devices is also available for example digitized pens.
These pens can be used as point devices or used to draw on graphics tablets. • Voice recognition could be the easiest way for data entry, but there is a big limitation with these devices. In voice recognition devices, a microphone is added on the VDU through some extra circuitry.
The unit senses the sound patterns and converts them to computer inputs. This method of input is especially useful when one cannot use their limps.
The function of optical scanner is to get documents into your computer with minimum time. They transform a letter, a logo, a photograph on paper into digital format that the computer can make sense of. Direct entry. They use the principle of light to sense the document contents.
There are many types of optical scanners such as Optical Character Recognition (OCR) and Optical Mark Reader (OMR). • Optical character recognition(OCR) is used to read utility bills such as electricity bill and water bill, insurance premium, and airline tickets.
Optical Scanning Wands: These are instrumental input devices that are used to read OCR coding on merchandise tags and other media, e.g. bar code reading. A bar code is a code that uses bars to represent characters.
The commonly used one is the Universal Product Code (UPC) that we see on products in our super markets. Information on the bars is sent to the database to identify the product record and read the details, including the price.
The price is sent back on the computer screen and printed on a receipt. An example of Universal Product Code can be seen in figure 3.2. This code is universal because it can be used all over the world.
Optical Mark Reader (OMR): These scanners are used to scoretests (like what is used to mark our KCPE exams). It reads predefined data positions that are marked, for example, by a pencil.
The marked position can then be sensed by the reader to transfer the predefined data value to go as computer input. • Magnetic Devices have magnetized information that can be recognized by the computer. An example is magnetic stripe and magnetic ink character readers.
Magnetic stripe helps computers to read credit cards, ATM cards etc. It is made up of iron-oxide coating materialwhich is the same as the one used on magnetic tape. Customer account numbers can be recorded on the magnetic stripe so that they can be read by banks authorization terminals.
Magnetic ink character recognition (MICR) read magnetically coded data. The documents are typed or printed using ink containing particles of iron oxide that gives them magnetic property.
An example is the computer systems in the banking industry that can magnetically read checks and deposit slips. An example of a check having magnetic characters can be seen in Figure 3.3.
Computers can sort out checks and post to different accounts because the identificationnumber of the bankand check no of customers account are written at the bottom of the page with an iron-oxide based ink, even signatures can be written with the same ink.
Read Sorters are used to read the checks. • There are many other computer input devices that don’t fit in the broad categories. • Examples of such devices are described below:
Digital Cameras: Digital still cameras and digital video cameras enable one to shoot, store and download still photos or full motion video with audio into the computer. They can use image-editing software to edit and enhance the digitized
image and include them in newsletters, reports, multimedia presentation, web pages etc. • Light Pen: This a pen like device that is light sensitive and is hand held. It is usually used as a design aid. It provides a direct input mode, which can be used in conjunction with a graphic VDU.
It is able to sense light shining on the screen, it can also be sensedata presented in the super markets using magnetic bars and strips. • Joystick: This is another direct input device, which is used to play computer games on domestic computers.
Key to Tape/Disk: This method of input uses storage media, in systems that have many users or a lot of input at once. The data coming is keyed on the storage medium and sent for processing at once, this makes the computer work on the data efficiently.
Figures 3.5 and 3.6 show examples of some of the devises used in the first generation. • The choice of data collection method and medium may be influenced by the following factors:
Appropriateness: Where is it conveniently used, for example MICR is largely confined to banking. • Cost: the largest cost is of staff, but also hardware
Time (response time): The faster the information gets into the computer, the quicker the response. • Accuracy: Input must be clean. Otherwise it will be rejected by the computer, and this either causes delays, or produces wrong output.
Volume of source data: Some methods cannot cope with high volumes of data within reasonable time scale.
The trend in input media as discussed before has been towards getting data as quickly as possible into the computer for processing that is, capturing data straight from the source. Figure 3.4 illustrates this trend.
1st Generation 2nd Generation 3rd Generation 4th Generation 5th Generation Punched Cards Paper Tape Punched Cards Key to Tape Key to Disk Key board Data Entry Pointing devices Optical Scanning Voice Recognition Touch Devices Hand activities recognition etc. (data capture methods) Trends of Input Technologies Figure 3.4
Figures 3.5 and 3.6 show some of the input devices used in the first an second generations, that is, a paper tape reader and a paper tape punch respectively.