CSEC Information Technology

Information Processing – Question 6!

1. DATA VS. INFORMATION – What’s the difference?

Data is raw unprocessed facts and figures. Information is data that has been processed. (i.e. makes sense, is in some order and is of some use)

Data: 1,1,2,4,5,2,1,1,4,,2

Information: four 1’s, three 2’s, two 4’s, one 5

2. SOURCES OF DATA – How do we get information to process?

• Forms

Forms can be used to collect information. These forms must be very clear however and not have any “vague”

sections. Data from forms then have to be entered into a computer. Errors may occur at this stage so double

data entry may be required. A document which contains data to be input is called a source document.

• Turnaround Documents

Turnaround documents are computer generated documents that leave space for a person to write or mark

information. The completed form is then fed back into the computer. OMR and OCR are used heavily for this

method of data capture. A lottery ticket is an example of a turnaround document.

• Data Logging

Data logging requires the use of sensors (light, heat, pressure) in a particular location to take readings over a

period of time. They are helpful in dangerous situations or when it is not desirable for a person to be taking

measurements by hand. Readings are then sent straight to a computer for analysis.

3. ERROR CHECKING

Many errors can occur when inputting information to be processed. Errors can be checked in two (2) ways.

Validation: The computerized checking for specific types of errors

Verification: The visual checking to make sure information entered or copied is ok

There are two main methods of verification:

• Double data entry - typing the data in twice. The two copies are automatically compared

• Proofreading data - This method involves somebody comparing what is on the screen to the document

4. ERROR CHECKING - VALIDATION

Validation is an automatic computer check to ensure that data entered is sensible and reasonable. It does not

check the accuracy of data. There are many different types of automatic checking. These include:

1. Format check

Checks to see if the data is in the right format.

e.g. A National Insurance number is in the form YYYYMMDD-9999

2. Length check

Checks the data isn't too short or too long

e.g. A password which needs to be six letters long

3. Presence check

Checks that data has been entered. In most databases a primary key field cannot be left blank

4. Range check

Checks that a value falls within a range

e.g. Number of hours worked must be between 0 and 50

5. Spell check

Looks up words in a dictionary when word processing

6. Data Type check

The correct type of data is entered in a data field

e.g. A number is entered in an AGE field rather than a word

7. Consistency check Checks two fields to see if they match School: DGS & Parish: Christ Church

Another example of consistency check is when you are asked to enter a password twice. This is

similar to double data entry of verification.

5. FILE ORGANIZATION AND ACCESS

Files may be arranged in random order, serial order, sequential order, alphabetical order or even in an

indexed order. Files can be accessed either directly or sequentially.

FILE ACCESS

Sequential file access means that information is accessed in the order it is received. Think of a cassette or

videotape. Information is stored in the order it is received. Rewinding/ fast forwarding is necessary

Direct access means that information is accessed/stored in any order. Think of a diskette or CD.

Information can be stored anywhere.

FILE ORGANISATION

Serial order – Records are arranged in the order that they are received

Sequential order – Records are arranged in ascending or descending order using a specified field (e.g. Last Name).

Index sequential – Records are given an index (number). Files are arranged in ascending or descending order based on the index.

Where a key or ID is used, this is referred to as the index.

32 Jones 29 Allan 29 Allan

29 Allan 40 Frank 32 Jones

40 Frank 32 Jones 40 Frank

6. TYPES OF FILES

Master file: A file which contains permanent information that does not change. (e.g. date of birth, name, bank account number)

Transaction file: A file that contains information which needs to be changed. (e.g. a daily bank record)

Update: The process of using the information from the transaction file to update the master file

Grandfather file: Also called the old master file. This is the oldest file left after updating.

For practice, look at any Question 6 from the past few exam papers.

Also try January 2014’s paper, #4

Random order

Alphabetical order

Index sequential

order