Producing robust programs

Question 1

Producing robust programs

What is Defensive Design?

Answer 1

Means that all possible contingencies are planned for including accidental or deliberate incorrect inputs or menu option selection

Question 2

Producing robust programs

What is this?
Means that all possible contingencies are planned for including accidental or deliberate incorrect inputs or menu option selection

Answer 2

Defensive Design

It ensures that
 Errors / bugs are kept to a minimum
 Programs behave as expected even if the user does something unexpected
 All possible errors that could occur are identified and catered for

Question 3

Producing robust programs

What does Defensive Design try to ensure?

Answer 3

 Errors / bugs are kept to a minimum
 Programs behave as expected even if the user does something unexpected
 All possible errors that could occur are identified and catered for

Question 4

Producing robust programs

Defensive Design

What is Input Sanitisation?

Answer 4

• Removing ‘white space’ from user input

* Converting user input so that it is all one case, e.g. upper case

Question 5

Producing robust programs

Defensive Design

What does this describe?
• Removing ‘white space’ from user input
• Converting user input so that it is all one case, e.g. upper case

Answer 5

Input Sanitisation

Question 6

Producing robust programs

Defensive Design
What is Validation?

Answer 6

• Range checks – checks input is between minimum and maximum values
• Data type checks – checks data, for example, is numeric / alphabetic
• Length check – checks data is a certain number of characters long
• Presence check – checks field is not empty, e.g. must enter a name

Question 7

Producing robust programs

Defensive Design

What is :

• Range checks – checks input is between minimum and maximum values
• Data type checks – checks data, for example, is numeric / alphabetic
• Length check – checks data is a certain number of characters long
• Presence check – checks field is not empty, e.g. must enter a name

Answer 7

Validation

Question 8

Producing robust programs

Defensive Design

What is Authentication?

Answer 8

• Authentication is the process of checking the identity of a user
• This is done using user names and passwords. Passwords will be stored in encrypted form
• Authentication checks that the username and password entered exist
• Using software such as reCaptcha to check that the user is human and not an online bot, automatically entering data in online forms

Question 9

Producing robust programs

Defensive Design

What is this?

• Authentication is the process of checking the identity of a user
• This is done using user names and passwords. Passwords will be stored in encrypted form
• Authentication checks that the username and password entered exist
• Using software such as reCaptcha to check that the user is human and not an online bot, automatically entering data in online forms

Answer 9

Authentication

Question 10

Producing robust programs

Defensive Design

How should you plan for contingencies? (4 things)

Answer 10

• Programs should check for potential errors such as division by 0
• Programs should give users options to Cancel requests / provide error messages
• Programs should not assume that a request to print has been successful so should always provide an option to reprint
• Programs accessing files should not assume that the file will be found or that a file has anything in it

Question 11

Producing robust programs

Defensive Design

What is this called?

• Programs should check for potential errors such as division by 0
• Programs should give users options to Cancel requests / provide error messages
• Programs should not assume that a request to print has been successful so should always provide an option to reprint
• Programs accessing files should not assume that the file will be found or that a file has anything in it

Answer 11

planning for contingencies

Question 12

Producing robust programs

Maintainability

Why do programmes need to be easy to maintain?

Answer 12

 So if you return to code to, for example, add more features, you can understand what you did
 So people who you are working with can pick up your code and easily work with and understand what you have done

Question 13

Producing robust programs

What are these?

 So if you return to code to, for example, add more features, you can understand what you did
 So people who you are working with can pick up your code and easily work with and understand what you have done

Answer 13

reasons why programmes need to be easy to maintain

Question 14

Producing robust programs

Maintainability

How can programmers ensure the code they write is easy to maintain?

Answer 14

 Use comments to:
• Explain the purpose of the program
• Explain sections of code
• Explain unusual approaches
• Visually divide sections of a program
 Use whitespace to make sections of a program easier to see
 Use indentations for every selection and iteration branch
 Use descriptive variable names and explain their purpose with a comment
 Use procedures and functions to:
• Structure the code
• Eliminate duplicate code
 Use constants declared at the top of a program

Question 15

Producing robust programs

Maintainability

What are these?
 Use comments to:
• Explain the purpose of the program
• Explain sections of code
• Explain unusual approaches
• Visually divide sections of a program
 Use whitespace to make sections of a program easier to see
 Use indentations for every selection and iteration branch
 Use descriptive variable names and explain their purpose with a comment
 Use procedures and functions to:
• Structure the code
• Eliminate duplicate code
 Use constants declared at the top of a program

Answer 15

ways programmers can ensure the code they write is easy to maintain

Question 16

Producing robust programs

Maintainability
How can the following help programmers ensure the code they write is easy to maintain?
comments (4 things)

Answer 16

	Use comments to:
•	Explain the purpose of the program
•	Explain sections of code
•	Explain unusual approaches
•	Visually divide sections of a program

Question 17

Producing robust programs

Maintainability

How can the following help programmers ensure the code they write is easy to maintain?
White space

Answer 17

 Use whitespace to make sections of a program easier to see

Question 18

Producing robust programs

Maintainability

How can the following help programmers ensure the code they write is easy to maintain?
Indentations

Answer 18

 Use indentations for every selection and iteration branch

Question 19

Producing robust programs

Maintainability

How can the following help programmers ensure the code they write is easy to maintain?
Descriptive variable names

Answer 19

 Use descriptive variable names and explain their purpose with a comment

Question 20

Producing robust programs

Maintainability

How can the following help programmers ensure the code they write is easy to maintain?

Procedures and functions

Answer 20

 Use procedures and functions to:
• Structure the code
• Eliminate duplicate code

Question 21

Producing robust programs

Maintainability

How can the following help programmers ensure the code they write is easy to maintain?
 constants

Answer 21

 Use constants declared at the top of a program

Question 22

Producing robust programs

Maintainability

How can the following help programmers ensure the code they write is easy to maintain?
 constants

Answer 22

 Use constants declared at the top of a program

Question 23

Producing robust programs

Testing

Four main reasons why a program should be thoroughly tested before being given to a user

Answer 23

1) To ensure there are no bugs or errors in the code

2 To ensure the program has an acceptable performance and usability

3) To ensure that unauthorised access is prevented
4) To ensure that the program meets the requirements

Question 24

Producing robust progroams
What are these?
1) To ensure there are no bugs or errors in the code

2 To ensure the program has an acceptable performance and usability

3) To ensure that unauthorised access is prevented
4) To ensure that the program meets the requirements

Answer 24

Four main reasons why a program should be thoroughly tested before being given to a user

Question 25

Producing robust programs Testing What is Iterative testing?

Answer 25

1) Performed when the software is being developed 2) Each new module is tested as it is added 3) Checking new modules do not introduce new errors into existing code 4) Tests to ensure the program handles erroneous data and exceptional situations

Question 26

Producing robust programs Testing What is this? 1) Performed when the software is being developed 2) Each new module is tested as it is added 3) Checking new modules do not introduce new errors into existing code 4) Tests to ensure the program handles erroneous data and exceptional situations

Answer 26

Iterative testing

Question 27

Producing robust programs What is Final / Terminal testing?

Answer 27

1) Performed when the program is considered complete 2) Testing that all modules work together (integration testing) 3) Testing the program produces the required results with all data types 4) Checking the program meets the requirements with real data, e.g. with a beta test