Selection (Cambridge International AS Computer Science)

What is selection?

• Selection is when the flow of a program is changed, depending on a set of conditions

• The outcome of this condition will then determine which lines or block of code is run next

• Selection is used for validation, calculation and making sense of a user's choices

• There are two ways to write selection statements:

  • if... then... else...
  • case...

If statements

Spec point — 11.2.2

What is an if statement?

• An If statements allow you to execute a set of instructions if a condition is true
• They have the following syntax:

Nested if statements

• Nested if statements are an if statement within an if statement
• Nested means to be 'stored inside the other'

Example code

If statements in different languages

Case statements

What is a case statement?

• A case statement can mean less code but it only useful when comparing multiple values of the same variable
• If statements are more flexible and are generally used more in languages such as Python
• The format of a CASE statement is:

Example code

Case statements in different languages