What are the common data types and data structures, and how are validation and verification used to keep data correct?
The common data types, the use of data structures such as arrays and records, and the difference between validation and verification.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on data organisation, covering the common data types (integer, real, Boolean, character and string), data structures such as arrays and records, and the difference between validation and verification with examples of each technique.
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What this topic is asking
WJEC wants you to know the common data types, how data structures such as arrays and records are used, and the difference between validation and verification. This is part of the Organisation and structure of data content in Unit 1 of WJEC GCSE Computer Science (3500).
Common data types
Data structures: arrays and records
Validation
Verification
Try this
Q1. State a suitable data type for storing whether a user is over 18. [1 mark]
- Cue. Boolean (true or false).
Q2. Name one validation check and describe what it does. [2 marks]
- Cue. A range check ensures a value lies between set limits (for example a percentage between 0 and 100).
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC-style Unit 14 marksState an appropriate data type for each of the following and justify one choice: a person's age, a price in pounds and pence, whether a box is ticked, and a surname.Show worked answer →
A Unit 1 data-types question. A person's age is a whole number, so the data type is integer (1 mark). A price in pounds and pence has a decimal part, so the data type is real (also called float) (1 mark). Whether a box is ticked has two states, so the data type is Boolean (true/false) (1 mark). A surname is text, so the data type is string (1 mark for the type with a justification, for example "a surname is a sequence of characters so it is a string"). Markers reward the correct type for each, with at least one justified. A common error is to store a price as an integer, which loses the pence, or to store age as a string.
WJEC-style Unit 14 marksExplain the difference between validation and verification, giving one example of each.Show worked answer →
A Unit 1 data-integrity question. Validation checks that entered data is sensible and follows set rules, for example a range check that an age is between 0 and 120, a presence check that a required field is not blank, or a format check that a postcode fits the right pattern (1 mark for the definition, 1 mark for a valid example). Verification checks that data has been entered or copied correctly, for example double entry (typing a password twice and comparing) or a visual check against the original document (1 mark for the definition, 1 mark for a valid example). Markers reward "sensible/follows rules" for validation and "entered correctly" for verification, plus an example of each. A common error is to say validation guarantees the data is correct, when it only checks it is reasonable.
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