1. Data entry: Validation
AS Level ICT
Data entry: Validation
Unit 1 Topic d - Data entry - Validation

2. Validation
Validation is a check that is carried out during the process of data entry
It is also the process by which data is accepted as being sensible and reasonable in the context within which it is being used
Validation is performed by the computer program that is in use, and consists of a series of checks that are called validation checks
Unit 1 Topic d - Data entry - Validation

3. Validation checks
Validation checks are used to restrict the data that can be entered so that it complies with the data rules that have been laid down
There are several different type of validation check that can be used, each of which has specific uses
Unit 1 Topic d - Data entry - Validation

4. Validation checks These validation checks include: Data type checks
Presence checks
Length checks
File/Table lookups
Cross field checks
Range checks
Unit 1 Topic d - Data entry - Validation

5. Validation checks These validation checks include: Format checks
Check digits
Parity checks
Spell checkers
Grammar checkers
Custom dictionaries
Unit 1 Topic d - Data entry - Validation

6. Data type checks
Character type checks make sure that the correct type of data has been entered
Example:
A letter has been entered into a database field that has been pre-set so that only it will only accept numerical data
The incorrect data type triggers a warning message and will not allow further data to be entered until the error has been corrected

7. Data type checks

8. Presence checks
Presence checks ensure that data that must be entered is entered
Example:
An online application form for a job requires the applicant to include their National Insurance number
If that was not entered the presence check would detect this and notify whoever was entering the data

9. Length checks
A length check makes sure that the number of characters entered into field matches that fields requirements
Example:
A National Insurance number will have two letters, followed by six numbers, followed by one letter (e.g. YY232425A)

10. Length checks
If this data is entered into a field specially set up to only accept data that is nine characters long, a length check will immediately identify if more or less than that number of characters has been entered

11. File/Table lookups
A lookup table contains a list of valid codes that can be used to enter data
If a code that is not in the lookup table is entered, it is rejected
This prevents any incorrect data from being processed

12. File/Table lookups Example:
A data management system for a restaurant uses lookup tables that contain the codes for each course that can be ordered

13. File/Table lookups
Code
Description
Price

14. File/Table lookups
When the unique code is entered, the item description and price are automatically entered
The system prompts the user to enter a correct code and does do allow incorrect codes to be entered

15. Cross field checks
Cross field checks occur when data in one field needs to be checked against data in another field in order for it to make sense
The simplest forms of cross field checks depend upon the use of check boxes, radio buttons, and/or drop down lists
In this cases it is simple for the cross field checks to take place

16. Cross field checks Example:
The salutation field on a record contains the value ‘Mrs’ but the gender field has been ticked to show the gender is ‘Male’
The cross field check would identify this anomaly and should flag the record up for checking

17. Range checks
Range checks make sure that numerical data falls between pre-determined limits (i.e. within a certain range of numbers)
Example:
Data about a pensioner is being added to a database
The bottom limit of the age range is 65
If the age is entered as 56, the range check will display this as an error because the age falls outside the pre-determined limits

18. Check digits
When large numbers are entered into a data system there is always a chance of error
To help to overcome this problem an additional number is often added to the end of the original number
This number is a check digit, and is calculated from the other numbers in the original number

19. Check digits Example: Check digits are found on barcodes
When the barcode is scanned, the computer automatically removes the end number and uses the rest of the numbers to calculate what the check digit should be
If the result is the same, then the number has been entered correctly

20. Check digits Example: The first number (4) is the check digit
Starting from the left, the next number (7) is multiplied by 11, the second (8) by 10, and so on
The total is then found: 7 x x x x x x x x x x x 1 = 315

21. Check digits
Example:
315 is then divided by 11 (there are 11 numbers) and the answer is 28 with a remainder of 7
The remainder is then deducted from 11 and the result should equal the check digit (11 – 7 = 4)
As the check digit is 4, the barcode has been entered correctly

22. Format checks
A format check ensures that data conforms to the requisite combination of characters
It achieves this by the use of a data input mask
Example:
A field in a data management system has been allocated so that National Insurance numbers can be inputted into it
The field has a data input mask that will only allow data that follows the correct combination of letters and numbers (e.g. YY232425A [LLNNNNNNL]) to be entered

23. Parity checks
When data is transmitted from one computer to another it is important that does not become damaged or ‘corrupted’ during transmission
Parity checking is a means of doing this
Parity is the sum of the bits within a piece of data
A parity error occurs when one of the bits is changed

24. Parity checks Example:
Data is being transmitted via a data link from one computer to another
During the transmission of the data there is an interruption
This may not be noticed by anyone using either computer, but a parity check will alert them to the fact that data is incomplete or corrupted

25. Spell checks Most computer applications have a spell check function
This spell check function can usually be ‘enabled’ (switched on) so that it can check the spelling of data as it is entered and automatically identify any mistakes

26. Spell checks
The spell check function can – in some applications – be enabled to automatically correct what appear to incorrect spellings, but this option should always be used with caution as it may lead to words that are not recognised but that are spelt correctly being ‘corrected’
Example:
An spell checker set to correct spelling ‘mistakes’ automatically changed a person’s surname from ‘Connew’ to ‘Conned’ – it replaced the correct spelling with another, incorrect word

27. Grammar checks
The grammar check function can – in word processing applications – be enabled to identify what appears to be the use of incorrect grammar, and to suggest alternatives

28. Grammar checks
Example:

29. Custom dictionaries
If a spell check function is enabled it should automatically identify any words that it does not recognise
Spell checkers often fail to recognise proper names (i.e. the names of people or places) or specialist words or jargon
It is possible to avoid this by setting up customised dictionaries to which words can be added
Once a word had been add to the customised dictionary, the spellchecker will recognised the new words as being spelt correctly

30. Custom dictionaries Example:
A spell check identifies the surname Bellingham as a spelling mistake
Once that surname is added to the custom dictionary, it is no longer identified as a spelling mistake as it is now on the list of correctly spelt words that the spell check function checks against

31. Data entry: Validation
AS Level ICT
Data entry: Validation
Unit 1 Topic d - Data entry - Validation