2.3 Producing robust programs

Question 1

Defensive design

Answer 1

the practice of planning for contingencies in the design stage of project or undertaking

Question 2

Anticipating misuse

Answer 2

the ability of a programmer to consider how the end user might accidentally (or on purpose) break the program and then write additional code to handle these situations

Question 3

Authentication

Answer 3

Verifying a user identity before they can use a program with a username and password

Question 4

What must a strong password have? (authentication)

Answer 4

they must be over a certain length with symbols and mixed case are advised

Question 5

Input validation

Answer 5

ensuring data input by the user meets the specific criteria before processing

Question 6

Examples of input validation (5)

Answer 6

range check, type check, presence check, format check and length check

Question 7

Maintainability

Answer 7

a selection of techniques and methods that make code easy to debug, update and maintain

Question 8

Naming conventions

Answer 8

many programmers use certain naming conventions for their variables/ procedure names

Question 9

Indentation

Answer 9

this makes it easy to see where structures begin and end
conditions and iterations should be indented
code inside procedures and functions should be indented

Question 10

Commenting

Answer 10

this is used by programmers to explain sections of code which make it easier to understand the program
the comments are ignored by the complier

Question 11

Testing

Answer 11

this is testing the program under various conditions to make sure it is going to work
you need to think about what devices it could be used on and what might cause the rash

Question 12

Iterative testing

Answer 12

each module is tested while it is being developed

Question 13

Final/ terminal testing

Answer 13

testing that all the modules of the program work together as expected
checking the program meets the expectations of the user with real data

Question 14

Syntax error

Answer 14

when the rules of the language have been broken so the program will not run

Question 15

Examples of syntax error

Answer 15

variables not being declared before use
incompatibility of variable types

Question 16

Logical error

Answer 16

the program runs but does not give the expected output

Question 17

Examples of logic error

Answer 17

division by zero, infinite loop, memory full, file not found

Question 18

Test data

Answer 18

values used to test a program, includes normal test data, boundary test and erroneous test data

Question 19

Test data : normal

Answer 19

data applied to a program which you would expect

Question 20

Test data : boundary

Answer 20

data supplied to a program which is designed to test the boundaries of a problem

Question 21

Test data : invalid

Answer 21

data of the correct type but outside accepted validation limits

Question 22

Test data : erroneous

Answer 22

data of the incorrect type which should be rejected by a computer system