Cambridge Syllabus Notes

📚 Cambridge IGCSE Computer Science 0478 – Programming

🔢 Objective: Understand and use basic data types

In programming, a data type tells the computer what kind of value a variable holds. Think of it as a label on a box that tells you whether the box contains a number, a letter, a true/false flag, or a whole sentence.

🧪 The Five Core Data Types

Type	Typical Value	Example in Java
Integer (int)	Whole numbers (e.g., 42, -7)	int age = 15;
Floating‑point (float, double)	Numbers with decimals (e.g., 3.14, -0.001)	double pi = 3.14159;
Character (char)	A single letter or symbol (e.g., 'A', '9', '&')	char grade = 'A';
String (String)	A sequence of characters (e.g., "Hello, world!")	String name = "Alice";
Boolean (boolean)	True or false	boolean isReady = true;

💡 Analogies to Make It Stick

Integers: Like counting apples – you can only have whole apples, no fractions.
Floating‑point: Like measuring liquid in a glass – you can have 0.5 liters, 1.75 liters, etc.
Characters: Like a single letter on a playing card.
Strings: Like a sentence written on a sticky note.
Booleans: Like a traffic light – either red (false) or green (true).

🧠 Key Points to Remember

Each data type has a specific size in memory (e.g., int is usually 4 bytes).
Variables must be declared with a type before they can be used.
Type mismatch errors occur when you try to store a value in the wrong type (e.g., assigning a string to an int).
Java automatically converts smaller numeric types to larger ones (widening) but not vice versa (narrowing) without explicit casting.
Use String for any text, even if it looks like a number (e.g., "12345" is a string).

📌 Examination Tips

Tip 1: When asked to declare a variable, always include the data type first. Example: int score;

Tip 2: For floating‑point numbers, remember to add an f suffix for float (e.g., float x = 2.5f;) or use double by default.

Tip 3: Boolean expressions can be simplified using == and !=. Example: if (isReady == true) can be written as if (isReady).

Tip 4: When converting between types, use (type) casting. Example: int i = (int) 3.7; (i becomes 3).

Tip 5: Practice writing short snippets that mix types, e.g., concatenating strings with numbers: System.out.println("Score: " + score);

🔍 Quick Practice Questions

What data type would you use to store the letter 'Z'?
Write a line of code that declares a double variable named temperature and assigns it the value 98.6.
Explain why int x = 5.5; causes a compile‑time error.
Convert the string "123" to an integer in Java.

Keep practicing by writing small programs that use these data types. The more you play with them, the easier they become!

Understand and use basic data types