AS Level ICT

1. AS Level ICT 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

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

4. Validation checks These validation checks include: Data type checks Presence checks Length checks File/Table lookups Cross field checks Range checks

5. Validation checks These validation checks include: Format checks Check digits Parity checks Spell checkers Grammar checkers Custom dictionaries

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