Programming Concepts

Question 1

What is the purpose of thinking ahead?

Answer 1

To make programs easy and intuitive for users to use.

Question 2

Define inputs.

Answer 2

Any data that is required to solve a problem usually entered into the system by the user.

Question 3

Define outputs.

Answer 3

The results that are passed back once the inputs have been processed and the problem solved.

Question 4

What three considerations do programmers need to make about inputs and outputs when thinking ahead?

Answer 4

• Method of input/output device used

Question 5

• Data structures used

Question 6

• Data types used

Question 7

• Order of data

Question 8

Identify the inputs likely to be used in a book reservation system at a library.

Answer 8

• Book details: name author ISBN

Question 9

• Borrower details: name library card number

Question 10

Identify the outputs likely to be used in a book reservation system at a library.

Answer 10

• Expected waiting time

Question 11

• Confirmation

Question 12

• Availability at other libraries

Question 13

• Collection point

Question 14

What are preconditions?

Answer 14

Requirements which must be met before a program can be executed.

Question 15

Where can preconditions be defined?

Answer 15

Within the code or within documentation.

Question 16

Give an example where preconditions are required.

Answer 16

• Stack functions: Check that a stack is not empty when popping an element from a stack.

Question 17

• Check that a stack is not full when pushing an element onto a stack.

Question 18

• Factorial function: The number passed to the function cannot be negative.

Question 19

State two advantages of including preconditions within the documentation accompanying a subroutine.

Answer 19

• Reduces the length of the program

Question 20

• Reduces the complexity of the program

Question 21

• Saves time needed to debug and maintain a longer program

Question 22

• Makes subroutine more reusable.

Question 23

Define caching.

Answer 23

The process of storing instructions or values in cache memory after they have been used as they may be used again.

Question 24

How is caching used in storing web pages?

Answer 24

Web pages that a user frequently accesses are cached so the next time one of these pages is accessed content can be loaded without any delay.

Question 25

What are the advantages of caching web pages?

Answer 25

• Content can be loaded without delay

Question 26

• Images and text do not have to be downloaded again multiple times

Question 27

• Frees bandwidth for other tasks on a network

Question 28

• Less time is spent waiting.

Question 29

What is the name given to the technique in which algorithms are used to predict which instructions are likely to soon be used?

Answer 29

Prefetching.

Question 30

Give a limitation of caching.

Answer 30

• Accuracy of the algorithms used

Question 31

• Effectiveness of algorithm in managing the cache

Question 32

• Size of the cache.

Question 33

Give three advantages of using reusable program components.

Answer 33

• More reliable than new components as they have already been tested.

Question 34

• As developing from scratch is not required this saves time money and resources.

Question 35

Give two examples of reusable program components.

Answer 35

• Abstract data structures e.g. queues and stacks.

Question 36

• Classes

Question 37

• Subroutines.