1/2 - Programming Fundamentals

AQA A-Level Computer Science

What is exception handling?

Writing code to anticipate possible errors and deal with them gracefully.

What is a subroutine?

A block of code with an identifiable, unique name within a program which breaks down a large problem.

Difference between procedure and a function.

Functions return a value.

What are advantages of suborutines?

• Easier to debug

• Creates reusable methods

• Can be grouped in libraries for easy reuse across programs

What is a stack frame?

A frame containing information about a subroutine.

What is included within a stack frame?

Return address, local variables, subroutine parameters

What is stack overflow/underflow?

Overflow: Trying to push a stack onto a frame with no space nor memory left.

Underflow: Trying to pop off a stack from an empty frame.

Why do local variables in functions lose their values?

They are destroyed with the stack.

What is recursion?

When a subroutine calls itself from within its own subroutine.

Characteristics of recursion (3)

• Contains a stopping condition (base case)

• For other inputs, the program should call itself

• Base case must be reachable within a finite number of loops

Why is recursion rarely used?

Consumes more memory in comparison to iterative approaches.

• The processor has to recall all the return addresses.