The use of data types Integer Real Boolean Character and string Casting

The idea

Data types classify values so a program stores and processes them correctly. Integer holds whole numbers such as 42 or -7; real holds decimals such as 3.14 or -0.5; Boolean holds only True or False; character holds one symbol such as 'A' or '7'; string holds text such as "Hello". Casting converts a value from one type to another, for example int("25") turns the string "25" into the integer 25, while str(25) turns 25 into "25". Casting is essential when input arrives as a string but arithmetic is needed, or when joining numbers into output text. Choosing the wrong type causes errors: adding "5" + "3" concatenates to "53", not 8. Use int() for whole numbers, float() for decimals, str() for text and bool() for truth values, and validate input before casting.

What earns the marks

• Identifies integer as a whole number type used for counting and exact arithmetic, e.g. score = 10.
• Identifies real (float) as a type for numbers with fractional parts, e.g. price = 2.99.
• Identifies Boolean as a type with exactly two values, True and False, used for conditions and flags.
• Identifies character as a single symbol and string as a sequence of characters, e.g. 'A' versus "Apple".
• Explains that casting changes a value's type, e.g. int("7") produces 7 and str(7) produces "7".
• Applies casting to solve a problem, such as converting input before arithmetic or converting a number before concatenation.
• Recognises that invalid casts raise errors, e.g. int("hello") fails because the string is not numeric.

Common mistakes and how to put them right

• Treating a string of digits as a number.

  Put it right: Cast with int("5") + int("3") to get 8.

• Using a real where an integer is required, such as range(3.0).

  Put it right: Cast to int(3.0) or use an integer literal.

• Assuming Boolean accepts other values such as 1 or "yes".

  Put it right: Use only True and False, and cast with bool() only when the conversion rule is understood.

• Forgetting that character and string are different.

  Put it right: Choose the type that matches the data and the operations needed.

Exam tips

• Read the scenario and name the most suitable type for each value before writing code; justify with one short reason.
• When a question shows input followed by arithmetic, check whether casting is needed and state the cast explicitly.
• For casting questions, trace the value step by step and show the type after each conversion, not just the final value.
• Use British English spelling such as 'character' and 'Boolean', and write code in a clear, indented style.