2.1.2 - thinking ahead

Question 2

Why do we need preconditions?

Answer 2

To ensure the function never crashes.

Question 3

advantages of specifying preconditions

Answer 3

• Ensures that the user knows what checks must be carried out before calling the subroutine.
• If there are no preconditions, the user can be confident that necessary checks will be carried out in the subroutine itself, saving unnecessary coding, making it easier to debug and maintain.
• Makes the subroutine reusable.

Question 4

benefits of code reuse

Answer 4

• shortens development time
• saves system resources
• lowers development costs
• reduces redundant code

Question 5

advantages of pre-written routines

Answer 5

• Already compiled so they are tested and error free.
• Saves work for programmers, shortens overall development time and reduces costs.
• May be used multiple times.
• May have been written in a different source language.
• Allows the programmer to use other prorammers’ expertise and is a more standardised approach to coding.
• May require fewer developers to work on a project.

Question 6

caching

Answer 6

The temporary storage of program instructions or data that have been used once and may be needed again shortly.

Question 7

advantages of caching

Answer 7

Improves speed and efficiency.

Question 8

disadvantages of caching

Answer 8

• The nature of predictive logic means caching algorithms can be very complicated to implement.
• The wrong data is often fetched and cached, therefore it has to be removed/flushed.