2.3.1 - Defensive Design

Question 1

What is anticipating misuse

Answer 1

• Ensuring a program caters for all possible inputs no matter how far fetched they are
• This is done by sending messages to correct user inputs

Question 2

What is authentication and how is it proved

Answer 2

• A process used to verify the identity of the user so only the correct user can access data
• It can be proved by a PIN, username and password, biometrics or personal information e.g. mothers maiden name

Question 3

What is verification

Answer 3

Asking a user to input some information such as a password twice to ensure it is them
This is a part of authentication

Question 4

What is input validation and why is it needed

Answer 4

• Ensures data entered is reasonable and sensible and in the right format
• Reduces the risk of incorrect data crashing a program

Question 5

Types of validation checks

Answer 5

• Presence check
• Data type check
• Format check
• Length check
• Range check

Question 6

What is a presence check

Answer 6

• Makes sure a value is inputted and the user doesn’t accidentally leave something blank
• Example code: if answer != “ “ then

Question 7

What is a data type check

Answer 7

• Makes sure the data entered is of the correct type e.g, only integers are entered as an input

Question 8

What is a range check

Answer 8

• Checks the upper and lower boundaries to make sure the users input is inbetween sensible values e.g. age for a game is inbetween 7-99

Question 9

What is a length check

Answer 9

• Limits the data entered to make sure it is not too short or too long

Question 10

What is maintainability and methods of doing it

Answer 10

• Making sure a program is easy to undersand or to modify
• Indentation
• NAming conventions
• Using subprograms
• Commenting

Question 11

What is indentation

Answer 11

• Where some lines of code are forward a few spaces
• This is used in selections and iterations
• They make it easier for the programmer to see where these loops are

Python auto indents but some other programming languages don’t

Question 12

What are naming conventions

Answer 12

• Giving variables sensible names that reflects the purpose of the variable and the data it stores
• This allows other programmers to understand what the variables are used for

Question 13

What is commenting

Answer 13

• # or //
• Allows for English communication of what certain parts of the code does
• Documents the creator and who edits as well
• this allows it to be maintained long after it was created

Question 14

What are subprograms and the different types of subprograms

Answer 14

• Breaking the code into smaller parts with each subprogram having a set role to produce structure code
• Functions - used to read data, manipulate it and send it back to the main program (return)
• Procedures - performs a task but doesn’t return a value

Question 15

Advantages of subprograms

Answer 15

• Saves time - can be saved as separate modules and used in other programs
• Small so easy to write, test and debug
• Shorter programs - can be called multiple times and only has to be written once