11.2 Constructs

2026 Syllabus Objectives

By the end of this subtopic, you should be able to:

  • write pseudocode for an IF statement with an ELSE clause
  • write pseudocode for nested IF statements
  • write pseudocode for a CASE structure
  • write pseudocode for a count-controlled loop
  • write pseudocode for a post-condition loop
  • write pseudocode for a pre-condition loop
  • explain why one type of loop may be more suitable for a problem than another

Main Content

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What are constructs?

In programming, a construct is a basic building block used to control what a program does. Constructs help a program make decisions and repeat actions.

In this subtopic, there are two main ideas:

  • selection — choosing between different actions
  • iteration — repeating actions using loops

These are very important in pseudocode because they let you write clear instructions for solving problems.

Selection

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What is selection?

Selection means the program chooses what to do next based on a condition.

A condition is something the program checks. The result is either true or false.

For example:

  • Is the mark greater than 49?
  • Is the username empty?
  • Is the choice equal to "Y"?

If the condition is true, one action happens. If it is false, a different action may happen.

Selection is useful when a program needs to:

  • validate input
  • compare values
  • respond to a user’s choice
  • decide which message to show

The two selection methods in this topic are:

  • IF statements
  • CASE statements

Relational operators

To write conditions, pseudocode often uses relational operators. These are symbols that compare values.

They produce a result of true or false.

Common relational operators are:

  • = means equal to
  • <> means not equal to
  • > means greater than
  • < means less than
  • >= means greater than or equal to
  • <= means less than or equal to

Example:

Age >= 16

This checks whether Age is 16 or more. If it is, the condition is true.

IF statements

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What is an IF statement?

An IF statement is used when a program needs to make a decision.

The program checks a condition. If the condition is true, it carries out a set of instructions.

Sometimes there is only one possible action when the condition is true. Sometimes there is also another action for when the condition is false. That is where the ELSE clause is used.

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