Arithmetic Operators — Programming Concepts | IGCSE Computer Science

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 13% of your exam marks.

stable

High

Stable13%

Paper 2 is almost entirely programming. Variable types, assignments, loops and conditionals are tested every session.

CIE pseudocode supports the standard arithmetic operators, plus two specific to integer division.

Operation	Pseudocode	Python
Addition	`+`	`+`
Subtraction	`-`	`-`
Multiplication	`*`	`*`
Division

CIE pseudocode uses only these operators: +, -, *, /, and the two integer-division operators MOD and DIV. There is no exponentiation operator in CIE pseudocode, so repeated multiplication is written out (for example x * x * x for "x cubed").

DIV: integer division

DIV returns the whole-number part of a division, throwing away any remainder.

17 DIV 5 = 3      (because 17 ÷ 5 = 3 remainder 2)
20 DIV 4 = 5      (because 20 ÷ 4 = 5 exactly)
9  DIV 2 = 4      (because 9 ÷ 2 = 4 remainder 1)

Useful for splitting things into equal groups: "how many full minutes are in 130 seconds?" → 130 DIV 60 = 2.

MOD: remainder

MOD returns the remainder after a division.

17 MOD 5 = 2      (17 ÷ 5 = 3 remainder 2)
20 MOD 4 = 0      (20 ÷ 4 = 5 remainder 0)
9  MOD 2 = 1      (9 ÷ 2 = 4 remainder 1)

Useful for a classic check: "is N divisible by 2?" → N MOD 2 = 0 is true for even numbers.

ROUND: rounding to a number of decimal places

ROUND(value, places) returns value rounded to places decimal places.

ROUND(3.14159, 2) = 3.14      (two decimal places)
ROUND(8.6, 0)     = 9         (zero decimal places: nearest whole number)

value should be a real number and places a whole number. ROUND is useful for tidying up money or measurements before they are output.

RANDOM(): a random number

RANDOM() returns a random real number between 0 and 1 inclusive. It takes no arguments.

To get a random whole number in a range, scale the result and round it. For example, a random whole number from 0 to 6 is ROUND(RANDOM() * 6, 0). RANDOM() is the standard way to add chance to a program, such as rolling a dice or shuffling.

Worked example

Using DIV and MOD together to split a total

A checkout system stores a total price in whole pence. Convert 503 pence into pounds and pence (e.g. £5.03).

Solution:

Whole pounds = 503 DIV 100 = 5 (integer quotient: how many complete hundreds fit)
Remaining pence = 503 MOD 100 = 3 (the remainder after removing those complete hundreds)
Result: £5.03

The same pattern applies any time a total must be split into a larger unit and a leftover: total items DIV group-size gives the number of complete groups; total items MOD group-size gives what is left over.