2.3 Producing Robust Algorithms

Question 1

Robust program

Answer 1

A program that is fault-tolerant and difficult to break/crash.

Question 2

Defensive design

Answer 2

programs should be designed to be robust and to not crash if a user does something unexpected.

Question 3

Defensive design considerations

Answer 3

• Input sanitisation/validation
• Anticipating misuse
• Authentication

Question 4

Input sanitisation/validation -

Answer 4

validation checks such as length checks and format checks can help to avoid causing errors.

Question 5

Anticipating misuse -

Answer 5

assume that users will try to break the program.

Question 6

Authentication

Answer 6

using logon systems with passwords to make sure the user is who they say they
are.

Question 7

Iterative testing -

Answer 7

testing that is carried out during production.

Question 8

Final/terminal testing -

Answer 8

Carried out just before the final program is released.

Question 9

Testing techniques

Answer 9

• Test with erroneous data
• Test with valid data
• Test with boundary data

Question 10

Erroneous data -

Answer 10

Data that is not valid.

Question 11

Boundary data

Answer 11

Data ‘on the edges’ of being acceptable

Question 12

Logic errors

Answer 12

Errors that mean your code works but not as intended e.g < instead of >. These will not be picked up by the IDE.

Question 13

Maintainability

Answer 13

Ensuring that code is easy to follow and repair/improve/edit.

Question 14

Ways of making code more maintainable -

Answer 14

Comments, indentation, meaningful variable names and use sub-routines.