CS / AS level

Programming and software development

Procedures, functions, parameters and structured control flow allow programs to be decomposed. Scope defines where names are visible; pass-by-value and reference-like behaviour affect which changes reach the caller.

Learning objectives

Explain programming and software development using a concrete example.
Apply the worked method and justify each step.
Recognise the limitation described in the final check.

The big idea

Requirements, design, implementation, testing and maintenance form a development process. Choose tests from specifications and risks, not only examples that the implementation already handles.

Worked example

A function returns n×n. What is returned for n=5?

Follow the solution

Substitute 5 into the defined expression: 5×5=25.

Investigate and explain

Predict the worked result before calculating. Change one input, record the new result, and explain which assumptions still hold.

Use the prediction activity below; a local model appears only where it supports this topic.

Open the interactive investigation

Check your understanding

1. What is a local variable?

A variable stored only on a local network
A variable whose scope is limited to its block or subprogram
A global constant

Check the answer and reasoning

A variable whose scope is limited to its block or subprogram

Local scope limits where the name can be used.

2. A function returns n×n. What is returned for n=5?

Check the answer and reasoning

Substitute 5 into the defined expression: 5×5=25.

3. Should invalid inputs be included in testing?

Yes
No
Only after release

Check the answer and reasoning

Yes

A robust specification includes rejection or handling of invalid data, which must be tested.