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created 23 days ago

Variables, Constants & Data Types Explained (O Level Computer Science 2210 / IGCSE 0478)

What Are Variables?

A variable is a named storage location in memory used to store data that can change during program execution.

Variables allow programs to store and manipulate information while the program is running.

Example:

score ← 85

In this example:

  • score is the variable

  • 85 is the value stored in that variable

Variables can change values as the program runs.

Why Variables Are Important

Variables are essential in programming because they allow programs to:

  • Store user input

  • Perform calculations

  • Track program data

  • Produce outputs

Without variables, programs would not be able to store or manipulate information.

What Are Constants?

A constant is a value that does not change during the execution of a program.

Constants are used when a fixed value must remain the same.

Example:

PI = 3.14

In this example, PI always remains the same value.

Constants help make programs more reliable and easier to understand.

Data Types

A data type defines the kind of data that a variable can store.

Different data types are used depending on the type of information being processed.

Common Data Types

Data TypeDescriptionExampleIntegerWhole numbers10RealNumbers with decimals3.14StringText characters"Hello"BooleanTrue or False valuesTrue

Using the correct data type ensures that programs handle data correctly and efficiently.

Examples of Variables and Data Types

Example pseudocode:

name ← "Ali"
age ← 16
temperature ← 36.5
isStudent ← TRUE

Explanation:

  • name → String

  • age → Integer

  • temperature → Real

  • isStudent → Boolean

Each variable stores a different type of data.

Why Data Types Are Important

Data types help programs:

  • Store data efficiently

  • Perform correct calculations

  • Prevent errors during program execution

For example:

You cannot perform mathematical operations on text strings.

Therefore, correct data types are necessary for proper program functionality.

Exam Tip (2210 / 0478)

Students are often asked to:

  • Define variable

  • Define constant

  • Identify data types

A common exam question is:

Explain the difference between a variable and a constant.

Practice Question

Explain one example of a Boolean data type.

Answer

A Boolean data type stores True or False values, which are often used in program conditions.

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