6.2 Data Integrity

2026 Syllabus Objectives

By the end of this subtopic, you should be able to:

  1. describe how data validation and data verification help protect the integrity of data

  2. describe and use methods of data validation, including:

    • range check
    • format check
    • length check
    • presence check
    • existence check
    • limit check
    • check digit
  3. describe and use methods of data verification during data entry and data transfer, including:

    • visual check
    • double entry
    • parity check for a byte
    • parity check for a block
    • checksum

What is data integrity?

Data integrity means data is accurate, complete, and unchanged unless it should be changed.

If data has integrity, it means:

  • it has been entered correctly
  • it has not been changed by mistake
  • it has not been damaged during transfer
  • it still makes sense for the purpose it is being used for

For example, if a student’s mark should be 78 but is entered as 87, the data has lost its integrity because it is no longer correct.

Data integrity is important because computer systems make decisions using data. If the data is wrong, the output will also be wrong. A school record, bank record, booking system, or medical file must all keep correct data.

Two important ways to protect data integrity are validation and verification.


Validation and verification: the difference

Students often confuse these two terms, so it is important to separate them clearly.

Validation

Validation checks whether data is reasonable and in the correct form.

Validation does not prove that the data is true. It only checks whether the data looks acceptable.

For example, if a person’s age is entered as 25, a validation check may accept it because it is a sensible number. But the computer still does not know whether the person is really 25.

Verification

Verification checks whether data has been copied, entered, or transferred correctly.

Verification is about checking that the data received is the same as the original data.

For example, if a name is written on paper as Amina Khan and typed into a computer as Amina Khan, verification helps confirm that the typed version matches the original.

Simple comparison

  • Validation asks: “Is this data sensible and in the right form?”
  • Verification asks: “Has this data been entered or transferred correctly?”

Both help protect data integrity, but they do different jobs.

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