GCSE Computer Science Revision — Variables & Data Types
Revise Variables & Data Types for GCSE Computer Science with a topic explanation, worked example and common mistakes. Check the board notes for specification differences.
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What is Variables & Data Types?
Variables are named memory locations used to store data that can change while a program is running. Each variable has a data type, which tells the computer what kind of data it can hold, such as an integer (whole number), a float (decimal number), a string (text), or a Boolean (True/False). Using the correct data type is crucial for writing efficient and error-free code.
Board notes: This is an absolute fundamental for all programming components of the AQA, Edexcel, and OCR specifications. You must know the common data types (Integer, Real/Float, String, Character, Boolean) and how to use them in the specified language.
Step-by-step explanationWorked examples
Worked example
In Python, to store a user's age: `userAge = 15`. Here, `userAge` is the variable name, and the value `15` is an integer. To store their name: `userName = "Alex"`. Here, `userName` is the variable, and `"Alex"` is a string. If we wanted to calculate their age next year, we could write `ageNextYear = userAge + 1`.
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Common mistakes
- 1Choosing the wrong data type, for example, storing a price like £9.99 as an integer instead of a float, which would lose the decimal part.
- 2Trying to perform operations on incompatible data types, like trying to mathematically add a string to a number without converting it first.
- 3Using unclear variable names like `x` or `temp`. Good variable names like `userAge` or `totalScore` make code much easier to read and understand.
Variables & Data Types exam questions
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Frequently asked questions
What is the difference between a variable and a constant?
A variable is a value that is expected to change during the program's execution. A constant is a value that, once assigned, should not be changed. Using constants for fixed values like the rate of VAT makes code more reliable.
What is casting in programming?
Casting is the process of converting a variable from one data type to another. For example, if you get a number as input from a user, it is often read as a string, so you need to cast it to an integer or float before you can use it in calculations.