Validation & Verification (Cambridge International IGCSE Computer Science)

Validation

Spec point — " (a) Understand the need for validation checks to be made on input data and the different types of validation check"

Validation

What is validation?

• Validation is an automated process where a computer checks if a user input is sensible and meets the program's requirements.

• There are six categories of validation which can be carried out on fields and data types, these are

  • Range check
  • Length check
  • Type check
  • Presence check
  • Format check
  • Check digit

• There can be occasions where more than one type of validation will be used on a field

• An example of this could be a password field which could have a length, presence and type check on it

Range check

• Ensures the data entered as a number falls within a particular range

Length check

• Checks the length of a string

Type check

• Check the data type of a field

Presence check

• Looks to see if any data has been entered in a field

Format check

• Ensures that the data has been entered in the correct format
• Format checks are done using pattern matching and string handling

Check digits

• Check digits are numerical values that are the final digit of a larger code such as a barcode or an International Standard Book Number (ISBN)
• They are calculated by applying an algorithm to the code and are then attached to the overall code

Verification

Spec point — "(b) Understand the need for verification checks to be made on input data and the different types of verification check"

Verification

What is verification?

• Verification is the act of checking data is accurate when entered into a system

• Mistakes such as creating a new account and entering a password incorrectly mean being locked out of the account immediately

• Verification methods include:

  • double entry checking
  • visual checks

Double entry checking

• Double entry checking involves entering the data twice in separate input boxes and then comparing the data to ensure they both match
• If they do not, an error message is shown

Visual checks

• Visual checks involve the user visually checking the data on the screen
• A popup or message then asks if the data is correct before proceeding
• If it isn’t the user then enters the data again

Worked Example Describe the purpose of validation and verification checks during data entry. Include an example for each.

[4]

Answers

Validation check

[1] for description:

• To test if the data entered is possible / reasonable / sensible
• A range check tests that data entered fits within specified values

[1] for example:

• Range / length / type / presence / format

Verification check

[1] for description:

• To test if the data input is the same as the data that was intended to be input
• A double entry check expects each item of data to be entered twice and compares both entries to check they are the same

[1] for example:

• Visual / double entry