Chapter 1.9 Handling of Data in Information Systems
1.9 (a) Manual and Automatic methods of Data Entry
All computer systems need to have data input to them otherwise they have nothing to process. The methods of collecting the data can be divided into two types: automatic and manual data collection.
Automatic Data Collection
The input devices used here are:
OMR: for multiple choice answer sheet marking
OCR: for scanning of documents that can be modified
MICR: for clearing bank cheques
Sensors: Here data will be captured in analogue form. Hence, there is a need for an Analogue-to Digital Converter to convert the data in digital form before sending to the computer.
1.9 (b) Methods of Image Capture
Scanner:
Used to convert printed text or graphics into digital form.
Video capture card
A video picture is made up of a series of images which are changed approximately 26 times per second in order to fool the brain into thinking that the images are moving. A video capture card is an interface board which fits into one of the expansion slots in a processor that allows the processor to store the values of the screen pixels for a specific picture. In other words it allows the action to be frozen. A typical example of the use of a video capture card is the market stall that uses a video camera to take an image of a customer and then to select one image to print onto a T shirt.
Digital camera
Works in a similar way to an optical camera but does not store the image on film. Instead, the image is stored electronically enabling the user to download it into a computer and manipulate the image and print out the images if desired.
Each of these image capture systems results in an electronic image being stored in the computer system. Image manipulation software can then be used to alter or edit the image in any way that is required. While this allows the user to use their imagination and to tidy up pictures or crop them to miss out unwanted parts of the image, it also allows unscrupulous people to produce pictures with very little foundation in reality. It used to be said that: “The camera never lies”, this is certainly no longer true, witness the film Forrest Gump.
1.9 (c) Validation and Verification
Verification
Verification means checking the input data with the original data to make sure that there have been no transcription errors. The standard way to do this is to input the data twice to the computer system. The computer then checks the two sets of data (which should be the same) and if there is a difference between the two sets of data the computer knows that one of the inputs is wrong. It won’t know which on is wrong but it can now ask the operator to check that particular input.
Validation
The first thing is to dispel a common misinterpretation of validation. In section 1.6.f checking of data was mentioned. Specifically, the use of parity bits to check data. This is NOT validation. Parity bits and echoing back are techniques that are used to check that data has been transmitted properly within a computer system (e.g. from the disk drive to the processor), validation checks are used to check the input of data to the system in the first place.
Validation is a check on DATA INPUT to the system by comparing the data input with a set of rules that the computer has been told the data must follow. If the data does not match up with the rules then there must be an error. There are many different types of validation check that can be used to check input in different applications.
1. Range check. A mathematics exam is out of 100. A simple validation rule that the computer can apply to any data that is input is that the mark must be between 0 and 100 inclusive. Consequently, a mark of 101 would be rejected by this check as being outside the acceptable range.
2. Character check. A person’s name will consist of letters of the alphabet and sometimes a hyphen or apostrophe. This rule can be applied to input of a person’s name so that dav2d will immediately be rejected as unacceptable.
3. Format check. A particular application is set up to accept a national insurance number. Each person has a unique national insurance number, but they all have the same format of characters, 2 letters followed by 6 digits followed by a single letter. If the computer knows this rule then it knows what the format of a NI number is and would reject ABC12345Z because it is in the wrong format, it breaks the rule.
4. Length check. A NI number has 9 characters, if more or fewer than 9 characters are keyed in then the data cannot be accurate.
5. Existence check. A bar code is read at a supermarket check out till. The code is sent to the main computer which will search for that code on the stock file. As the stock file contains details of all items held in stock, if it is not there then the item cannot exist, which it obviously does, therefore the code must have been wrongly read.
6. Check digit. When the code is read on the item at the supermarket, it consists of numbers. One number is special, it is called the check digit. If the other numbers have some arithmetic done to them using a simple algorithm the answer should be this special digit. When the code is read at the check out till, if the arithmetic does not give the check digit it must have been read wrongly, it is at this point that the beeping sound would normally be heard if everything is alright.
1.9 (d) Output Formats
When data has been processed by a computer system it is necessary to report the results of the processing. There are a number of different ways that the results can be reported to the user.
Graphs
Graphs show trends very clearly.
Reports
A report is a hard copy printout of the values of variables. This has the advantage of producing the actual figures according to the values specified by the user. However, the figures themselves may need skill to interpret their significance and the value of figures in a vacuum is often hard to justify.
Interactive presentations
The previous forms have relied on the format of the report being decided without the luxury of being able to see what the figures look like in the first place. If the system allows the user to decide the type and range of output required during the run then there is some positive user involvement leading to an interactive presentation where the user can adjust the output to suit their needs.
Sound
Many applications do not lend themselves to a standard, visual, printout. Sound can be used for output from some systems. Obvious examples would be voice synthesis for reporting to blind people and an alarm system to protect property against burglars.
Video
Video is a visually satisfying form of output that takes large amounts of memory to produce because the nature of the medium requires large quantities of pictures to produce the feel of continuous motion. Video is useful for demonstration of techniques where there is little value in pages of instruction if a simple video can illustrate something better.
Images
‘Images’ can refer to any of the forms of output mentioned when they are shown on a monitor screen, as opposed to the hard copy produced from a printer.
Animations
Provide a good stimulus for an audience and lead from one slide to another when making a slide based presentation. Animation takes considerably less processing power than other forms of motion, unless the image being animated is complex. Animation is used so often that it can come across as being a boring technique that has just been added for ‘gloss’.
Example Questions
1. a) State two methods of data entry used by banks in their cheque system. (2)
b) Explain why banks find the use of your two examples suitable for this application.
2. A small stall is to be opened, as part of a fairground, where the customer can have their likeness printed on to the front of a sweatshirt. Describe two possible methods of capturing the image to be printed. (4)
3. A mail order firm receives orders from customers on paper order forms. These are keyed into the computer system by operators. The data that is to be keyed in includes the 5 digit article number, the name of the customer and the date that the order has been received.
a) Explain how the data input would be verified. (3)
b) Describe three different validation routines that could be performed on the data. (6)
4. A reaction vessel in a chemical plant is monitored, along with many others, by a computer system using a number of sensors of different types. Describe three different types of output that would be used by such a system, stating why such a use would be necessary. (6)
5. Explain what is meant by the timeliness and relevance of data. (2)
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