National 5 Computing Science
Choosing the most suitable data type
National 5 Computing Science: Software design and development
"State the most suitable data type" is one of the commonest 1-mark questions in National 5 Computing Science. The word that matters is most suitable, and the examiners' reports for 2023 and 2025 show where pupils slip.
The five data types
| Data type | Holds | Examples |
|---|---|---|
| integer | whole numbers | number of tickets: 4; age: 15 |
| real | numbers that can have a decimal point | price: 9.50; time: 12.85 seconds |
| character | exactly one letter, digit or symbol | answer: Y; grade: B |
| string | text: any number of characters | name: Eilidh; postcode: IV2 3AB |
| Boolean | one of two values: true or false | is a member: TRUE |
The traps
- A single letter is a character, not a string. "Y or N" is a character.
- Phone numbers are strings. They are made of digits, but they can start with 0 and contain spaces, and you never do arithmetic with them. The same goes for postcodes and card numbers.
- Real only when a decimal point is possible. A number of tickets is an integer; a price is real.
- Dividing gives a real. In
SET average TO total / 4, the average is real even iftotalis an integer. - Use the proper names. "Number", "text" and "yes/no" do not gain the mark.
For a list of values the question may ask for the data structure and the data type separately. Thirty pupils' test scores are an array (the structure) of integers (the type).
The same idea in databases
If you study database design, the field types have different names (text, number, date, time, Boolean), but the phone number trap is the same: it is stored as text.
Try two exam-style questions
Choose an answer, say how sure you are, then press Check. Every wrong answer tells you why it is wrong.
The full course covers every topic like this. Every topic in National 5 Computing Science has a short note, a simulation to try and a practice quiz with feedback on every answer, plus coding lessons, a full mock exam and a progress report for parents.
More guides
- Input validation: how to get all 4 marks
- Running total within a loop
- round, random and length: writing the whole call
- Evaluating a program: answers that gain the mark
- Concatenation: joining strings for the mark
- Iterative development: describing going back
- Testing: test data and test tables
- All the free revision guides
This site is independent: it is not connected to the SQA or Qualifications Scotland. Points from the examiners' course reports are given in our own words.