Arithmetic operations in a programming language: real division

The idea

Real division divides one numeric value by another and keeps any fractional part, producing a real (decimal) result. In many languages it is written with the forward slash operator, so result ← 7 / 2 stores 3.5 rather than 3. Learners should distinguish real division from integer division, which discards the remainder. They should be able to evaluate a division expression, recognise when the result is real, and explain why dividing by zero is an error that a program must avoid. They should also trace a short program line and state the value assigned, and recognise real division inside a mixed expression where precedence applies.

What earns the marks

• Identifies the real division operator in a program line, typically the forward slash symbol.
• Correctly evaluates a division such as 7 / 2 as 3.5, keeping the fractional part.
• Distinguishes real division, which keeps the fraction, from integer division, which discards it.
• Explains that dividing by zero is an error and should be avoided in a program.
• Traces a short program and states the real value stored in a variable after a division statement.

Common mistakes and how to put them right

• Treating 7 / 2 as 3 by discarding the remainder.

  Put it right: Real division keeps the fractional part and gives 3.5.

• Confusing the forward slash with the integer division operator.

  Put it right: Check which operator the language uses for real division.

• Ignoring the possibility of division by zero.

  Put it right: Recognise it as an error the program must guard against.

Exam tips

• Write the full decimal result, not a rounded integer, when the question asks for real division.
• State clearly whether an operator performs real or integer division before calculating.
• Check for a zero divisor and say that the program would fail rather than give a value.