10.2 Thinking Ahead

Question 1

What is the ‘input’ in an abstract model?

Answer 1

The information relevant to the problem, which could for example be passed as parameters to a subroutine

Question 2

What is the ‘output’ in an abstract model?

Answer 2

The solution to the problem, which could be passed back from a subroutine

Question 3

Why is it important to think ahead?

Answer 3

Because the algorithm you are working on must be correct and it also must be efficient

Question 4

Advantages of documenting the inputs and outputs?

Answer 4

There is no ambiguity in what must be supplied to the sub-procedure and what is returned

Question 5

Advantages of specifying preconditions

Answer 5

• Makes program components reusable
• Cutting out unnecessary checks
• Makes programs easier to debug and maintain

Question 6

What are some examples of reusable program concepts?

Answer 6

Libraries and components

Question 7

List some typical standards for reusable modules

Answer 7

• Inputs, outputs and preconditions should be documented
• Variable identifiers should conform to a standard convention

Question 8

Cashing

Answer 8

Temporary storage of data and instructions

Question 9

Advantages of caching

Answer 9

• Faster access to cached resources
• Saving on costly use of bandwidth
• Reduced load on web services in a client-server environment

Question 10

Drawbacks of caching

Answer 10

• Slower performance if the resource isn’t found in the cache
• Could be given a stale copy of a resource when an up-to-date copy is needed