Unit 8 - Logic and languages

Question 1

What is the purpose of a truth table?

Answer 1

To show all possible inputs and the corresponding outputs

Question 2

What are the 5 types of defensive design?

Answer 2

• Input sanitation
• Validation
• Verification
• Authentication
• Maintainabe code

Question 3

What is input sanitation?

Answer 3

Input sanitisation cleaning up input data / removing
unwanted data e.g. removing special characters / preventing SQL injection

Question 4

What is validation?

Answer 4

Checking whether input data should be allowed / is sensible / follows criteria

Question 5

What are the 6 types of input validation checks?

Answer 5

• Range
• Type
• Presence
• Length
• Format
• Table

Question 6

What does a range check do?

Answer 6

checks boundaries

Question 7

What does a type check do?

Answer 7

making sure the data inputted is of the
correct data type

Question 8

What does a presence check do?

Answer 8

making sure a value is inputted / not
blank

Question 9

What does a length check do?

Answer 9

limit number of characters // check
maximum / minimum string length

Question 10

What does a format check do?

Answer 10

making sure the data inputted follows a
set pattern

Question 11

What does a table check do?

Answer 11

making sure the data inputted is one from an allowed set of values

Question 12

What is verification?

Answer 12

checks whether data has been entered correctly

Question 13

What is authentication?

Answer 13

Authentication ensures only authorised users can gain access e.g using password

Question 14

How does password routine work?

Answer 14

Commonly, you are asked to enter a User ID
and a password. Once you have entered the User ID, the website looks up your password in a database. If the user ID cannot be found, an error message is displayed

Question 15

What is program maintainablility?

Answer 15

It is important that programs are written in a way to make them easily maintainable to allow other programmers to understand the code.

Question 16

What are the 4 ways to maintain a program?

Answer 16

• Comments
• Meaningful variables
• Modularise
• Indentation

Question 17

How does commenting improve maintainability?

Answer 17

Enables programmers to understand the purpose of each line / section

Question 18

How does naming variales sensibly improve maintainability?

Answer 18

to enable programmers to understand the purpose of each variable

Question 19

How does modularisation improve maintainability?

Answer 19

allows reuse / makes easier to test / reduces errors e.g. create as a function

Question 20

How does indentation improve maintainability?

Answer 20

Indentation makes it possible to easily see which lines of code are part of different structures

Question 21

What are the 2 types of errors?

Answer 21

• Syntax error
• Logical error

Question 22

What is a logical error?

Answer 22

• An error that results in incorrect output / unexpected result
• Contains an error but still runs

Question 23

What is a syntax error?

Answer 23

• An error that breaks the rules of the programming language
• Contains an error but will not run / execute

Question 24

Why is testing important?

Answer 24

• Check the program works as intended and meets user requirements.
• gives the correct output / result
• detect errors

Question 25

What are the 5 types of testing?

Answer 25

- Final - Iterative - Normal - Boundary - Erroneous

Question 26

What is final testing?

Answer 26

Completed at the end of development to test the program as a whole.

Question 27

What is iterative testing?

Answer 27

.Completed during development after each module is completed. Tests module seperately.

Question 28

What is normal testing?

Answer 28

Test using data that should be accepted

Question 29

What is boundary testing?

Answer 29

Test using data that is on the edge of being acceptable / unacceptable. Test highest / lowest value

Question 30

What is erroneous testing?

Answer 30

Test using data that should be rejected

Question 31

What is the difference between final and iterative testing?

Answer 31

Iterative is during development and Final is when the development is complete.

Question 32

How do you identify logical errors?

Answer 32

Trace table

Question 33

What is a trace table?

Answer 33

A trace table is useful for tracing through a program in order to find a logic error. The value of each variable is recorded as it changes.

Question 34

What are trace tables useful for?

Answer 34

- Determining the purpose of an algorithm - Finding the output of an algorithm - Finding errors in an algorithm

Question 35

What are the 2 types of programming languages?

Answer 35

- High-level - Low-level

Question 36

What is assembly language?

Answer 36

- Assembly language is processor-specific - It has to be translated into machine code before it can be executed - As each instruction corresponds directly to a machine code instruction, it is known as a low-level language

Question 37

What are high level languages?

Answer 37

Uses English-like keywords such as print and while Must be translated before the processor can execute code. Code written is portable between different processors.

Question 38

What are advantages of high level languages?

Answer 38

Easier for humans to write. Easier/quicker to remember. Easier to maintain / debug because code uses English words.

Question 39

What is advantage of low level language?

Answer 39

- It allows the user to directly manipulate memory - A program can run very quickly - The code will usually require less RAM

Question 40

Why does high level language need to be translated?

Answer 40

The computer can only understand machine code.

Question 41

What are the 2 ways to translate high level language?

Answer 41

Compiler Interpreter

Question 42

How does a compiler work?

Answer 42

Compiler translates code in one go and produces an executable file

Question 43

How does an interpreter work?

Answer 43

Interpreter translates code line by line which will be translated every time it is run.

Question 44

Features of compiler

Answer 44

- Translate whole program = object code - Executes faster, already in machine code - Compiler doesn't need to be present to run object code - Code cannot be adapted

Question 45

Features of interpreter

Answer 45

- translates one line at a time - longer to execute - interpreter must be installed to run program - source code can be adapted -

Question 46

What are IDEs?

Answer 46

Provide tools and features that help programmers when programming

Question 47

What are the IDE tools provided? | 9 features

Answer 47

- Translator - Runtime environment - Error diagnostics - Breakpoints - Code editor - Keyword highlighting - Variable watch - Syntax suggestion - Stepping

Question 48

What does translator do?

Answer 48

converts the high level code into machine code to enable to code to be run

Question 49

What does runtime environment do?

Answer 49

allows program/code to be run + shows output of the program/code

Question 50

What does error diagnostics do?

Answer 50

identify location/detail of errors

Question 51

What does break points do?

Answer 51

will allow the program to stop at a chosen / set position

Question 52

What does code editor do?

Answer 52

allows program code to be written/changed + allows errors to be fixed

Question 53

What does keyword highlighting do?

Answer 53

allows keywords/variables to be coloured and identified

Question 54

What does variable watch do?

Answer 54

see the contents/data held in variables

Question 55

What does syntax suggestion do?

Answer 55

suggests/corrects code

Question 56

What does stepping do?

Answer 56

execute/run the program line by line