Topic 8 - Producing robust programs

Question 1

Structure diagrams

Answer 1

• they decompose the program into smaller, more manageable modules – that eventually perform individual tasks

Question 2

advantages of using structure
( E, LofP, R )

Answer 2

• coding is easier as you are only coding very simple tasks
• lots of programmers can work together as each module can be written independently
• can reuse sub programs in future programs

Question 3

defensive design

Answer 3

Defensive design ensures that programs function properly and never produce errors

Question 4

how do programmers try to protect their programs through defensive design?

Answer 4

• anticipate how users might misuse their program then prevent it
• ensure the code is well maintained
• reduce number of errors in code through testing

Question 5

Why is it important that code is well-maintained?

Answer 5

so it is easy for other programmers to understand what the code does, so they can use the code

Question 6

how can you make code more maintainable?

Answer 6

• Indentation
• Meaningful variable names
• Subroutines
• Comments

Question 7

Indentation

Answer 7

• groups together functions
• ## makes longer programs much easier to read and follow

Question 8

comments

Answer 8

• explains the code and its function in more detail
• using psuedocode that all programmers will understand
• can also inform other programmers of a bug or issues

Question 9

meaningful variable names

Answer 9

• variables should be named to refer to what they actually are
• they should also be easy to read and use capital letters and underscores to make it easier to read

Question 10

subroutines

Answer 10

they give a program structure
- easier to see how different parts of a program come together

Question 11

Input validation

Answer 11

checking if data meets certain criteria before passing it into the program

Question 12

types of input validation

Answer 12

• format check
• data type check
• length check

Question 13

verification

Answer 13

checks if the input has been entered correctly ( not double entry or no entry )

Question 14

authentication

Answer 14

method of confirming the identity of the user before allowing them access to the program

Question 15

how do programmers use authentication

Answer 15

• passwords associated with usernames
• biometrics
• limit the number of failed authentication attempts before access to an account is lost
• strong passwords

Question 16

Iterative testing

Answer 16

-program is tested as it is developed, line by line
- used to fix small errors which prevent larger errors later on

Question 17

final testing

Answer 17

-program is tested at the end of the development process
- modules may work perfectly on their own but errors may occur when the modules interact with each other

Question 18

what are errors?

Answer 18

mistakes in the program code that causes the program to run incorrectly

Question 19

logic errors

Answer 19

when the compiler/interpreter is able to run the program but produces an unexpected result

Question 20

syntax error

Answer 20

when the compiler/interpreter can’t understand a part of the program because it doesn’t follow the grammar/rules of the language

Question 21

how are logic errors diagnosed

Answer 21

they are harder to find as compilers/interpreters can’t pick them up.
- test plans & general use of program

Question 22

how are syntax errors diagnosed

Answer 22

by compilers/interpreters as they won’t be able to run the program and return a syntax error ( with location)

Question 23

test plan

Answer 23

anticipates all the potential issues with program and selects appropriate test data ( normal, boundary, erroneous, invalid )

Question 24

invalid data

Answer 24

values higher or lower than the expected range

Question 25

erroneous data

Answer 25

incorrect data types that the program shouldn’t accept