Defensive design

Question 1

Why is defensive design important?

Answer 1

• the number of errors or bugs is minimized
• the program behaves as expected despite unexpected user actions (accidental or deliberate erroneous inputs or item selections)
• all possible errors that could occur are identified and allowed for

Question 2

How is authentication used?

Answer 2

• the process of determining the identity of a user
• usually based on a username and an associated password
• authentication checks that the username and password exist

Question 3

What is validation used for?

Answer 3

validation process checks that data that is input is sensible, reasonable and appropriate to be processed by the program

-should be used to ensure that the required data is input, is within a certain range or of a required length

Question 4

presence check

Answer 4

ensures that data has been entered

Question 5

length check

Answer 5

length checks ensure that a specified number of characters have been entered

Question 6

range check

Answer 6

ensure that an input falls within the required range

Question 7

program

Answer 7

sequence of instructions for a computer

Question 8

What does planning for all contingencies mean?

Answer 8

planning for all possibilities

Question 9

areas of defensive design (3)

Answer 9

• protection against unexpected user inputs or actions
• maintainability - code is readable and understandable
• minimizing/removing bugs

Question 10

validation definition

Answer 10

checking data input is sensible and in the right format

Question 11

data sanitization

Answer 11

the process of hiding or protecting data so it cannot be seen or disclosed

Question 12

authentication

Answer 12

verifying the identity of a user

Question 13

maintainability

Answer 13

the process of ensuring that a program is easy to understand, modify and update

Question 14

testing

Answer 14

an important part of computer programming which involves checking a program for errors

Question 15

defensive design definition

Answer 15

contingency planning using validation, sanitization, authentication, maintenance, and testing

Question 16

examples of contingencies (6)

Answer 16

• maths errors, division by 0
• communication error, online systems need a connection to a server, if it’s lost the program should tell the user and resume when it returns
• printer/hardware error, there should be options to repeat an action/print again
• disk errors, the program should check that the file can be found, isn’t corrupted, and that there is space on the disk
• a user might misinterpret the on screen prompts
• they might enter data into the wrong input box