2.3 Producing robust programs

Question 1

what are the defensive design considerations

Answer 1

• anticipating misuse
• authentication

Question 2

one method of authentication

Answer 2

usernames and passwords can be entered. if they match previously stored entries for that user then access is granted

Question 3

what is anticipating misuse

Answer 3

trying to predict all possible inputs so that it will never crash or give an incorrect result

when validation or verification can’t solve the issue, help messages and careful instruction should be used

Question 4

what is authentication

Answer 4

making sure that a person is who they say they are

methods include usernames and passwords, fingerprint ID or facial recognition

Question 5

what is input validation

Answer 5

the checking of input data to ensure that it is sensible or reasonable. it cannot guarantee that the data is correct

Question 6

types of input validation

Answer 6

• range check
• length check
• type check
• presence check
• format check

Question 7

what is a range check

Answer 7

the input is within a specified range

Question 8

what is a type check

Answer 8

the input is the right data type

eg string, integer

Question 9

what things are important to the maintainability of a program

Answer 9

• use of sub programs
• naming conventions
• indentation
• commenting

Question 10

what is verification

Answer 10

the input of data twice to see if they match

Question 11

advantages of subprograms

Answer 11

• makes debugging the program easier as they are usually quite short
• they can be tested separately
• a particular subprogram can be called multiple times in the same program and be saved in a library to be used again in other programs
• helps to produce structured code

Question 12

example of decomposition in programming

Answer 12

using subprograms

Question 13

why do we use naming conventions and what does it involve

Answer 13

helps to identify variable names within a code
helps with readability

• having meaningful and consistent format for the naming of variables

eg camelCase

Question 14

why do we use indentation

Answer 14

helps the readability as it is then clear where statements within an iteration or other construct start and end. for some programming languages its mandatory

Question 15

why do we use commenting

Answer 15

used to document for yourself and others the purpose of the program and each subprogram. it can also indicate who wrote the program and when it was last updated

helps to ensure that the program can still be understood and maintained long after it was written

Question 16

the purpose of testing

Answer 16

to ensure that for any input, the program always runs correctly

Question 17

types of testing

Answer 17

iterative
final or terminal

Question 18

what is iterative testing

Answer 18

carried out using a pre-written test plan, finding and correcting errors in a program and retesting until all tests give the expected output

done during development

Question 19

what is final testing

Answer 19

checking that all the required functions have been included, nothing is missing and everything works correctly when data is entered

done when the program is completely finished

Question 20

what are the two types of errors in programming

Answer 20

syntax
logic

Question 21

what is a syntax error

Answer 21

errors which break the grammatical rules of the programming languages and stop it from being run

Question 22

what is a logic error

Answer 22

errors which produce an unexpected output but will still run

Question 23

what are the types of test data

Answer 23

normal
boundary
invalid/erroneous

Question 24

what is normal test data

Answer 24

data which should be accepted by a program without causing errors

Question 25

what is boundary test data

Answer 25

data of the correct type which is on the very edge of being invalid - using both ends of the allowed range

Question 26

what is invalid test data

Answer 26

data of the correct data type which should be rejected by the computer system

Question 27

what is erroneous test data

Answer 27

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