2.1.2 Thinking ahead

Question 1

What is Thinking Ahead?

Answer 1

• Considering issues you are likely to encounter in the future

Question 2

What are the features of Thinking ahead?

Answer 2

• Identify inputs and outputs
• Determine preconditions
• Caching
• Reusable components

Question 3

What are Preconditions?

Answer 3

• Requirements which must be met before a program can be executed
• Set on the data processed by the program
• Can be tested for within code but are more often included within documentation

Question 4

What are the advantages of specifying preconditions?

Answer 4

• Sepcifying preconditions withing documentation lets the user know what checks must be carried before calling subroutine
• Specifying within documentation reduces the length
  and complexity of the program
• Clear documentation helps make the subroutine reusable

Question 5

What is the need for Reusable Program Components?

Answer 5

• Commonly used functions are often packaged into libraries for reuse.
• Having components which are already written,debugged and tested will save time
• Simplified development process
• Compatibility issues may require components to be modyfied

Question 6

What is caching?

Answer 6

• Process of storing instructions or values in cache memory after they have been used, as they may be used again.
• Very common in the storage of web pages

Question 7

What are the advantages of caching?

Answer 7

• Saves time which would be needed to store and retrieve instructions from secondary memory
• Content of webpages can be loaded without any delay
• Images and text dont have to downloaded again, freeing up bandwidth

Question 8

What are the disadvtages of caching?

Answer 8

• Effectiveness of caching depends on how well a caching algorithm is able to manage the cache.
• Larger caches take long time to search so cache size limit how much data can be stored.