Computational Thinking (III) - Design, Testing and IDEs

Question 1

For a computer language to be processed what must happen?

Answer 1

It needs to be translated into machine code

Question 2

What are the advantages of high level programming languages?

Answer 2

They are close to the spoken and written language of the programmer making it much easier to work with

Question 3

Name some high level languages

Answer 3

Python

Java

C++

C#

Visual Basic

JavaScript

Question 4

Programs written in high level language are known as what?

Answer 4

Source code

Question 5

What are low level languages?

Answer 5

They sit close to the computer’s instruction set

Question 6

What are the two types of low level language?

Answer 6

Machine Code

Assembly Language

Question 7

What is machine code?

Answer 7

Instructions that a process understands and can act upon

Question 8

What are the advantages of writing in machine code?

Answer 8

More flexibility

Question 9

What are the disadvantages of writing in machine code?

Answer 9

Very difficult to write in, understand and debug (consisting of binary and hexadecimal)

Question 10

When programmers need direct control of machine code, what is used?

Answer 10

Another low level language – assembly language

Question 11

What does assembly language use?

Answer 11

Mnemonics, for example:

LDA – load a value from a memory address
STA – store a value in a memory address
ADD – adds the value held in a memory address to the value held in the accumulator
SUB – subtracts from the accumulators the value held in a memory address
MOV – moves the contents of one memory address to another

Question 12

What is Opcode and Operand?

Answer 12

Opcode – actual instructions

Operand – this is a value that the instruction uses or manipulates

Question 13

What are translators?

Answer 13

A program that converts source code (high level language written program) into object code (a form the computer understand)

Question 14

What are the three types of translator?

Answer 14

Compilers

Interpreters

Assemblers

Question 15

What is a compiler?

Answer 15

A compiler takes the source code as a whole and translates it into object code, in one go

Question 16

What is an interpreter?

Answer 16

An interpreter translates source code into object code one instruction at a time

Question 17

What is an assembler?

Answer 17

An assembler translates assembly language into object code

Question 18

What is an IDE?

Answer 18

Tools which are gathered together to help write programs

Question 19

What is the Python IDE?

Answer 19

IDLE

Question 20

What are editors?

Answer 20

Editors are software which allow programmers to write and edit code. Editors are often fairly simple, but usually offer facilities such as:

Automatic line numbering
Colour coding
Auto-correct
Auto-suggest
Auto-indent

Question 21

What do editors help with (and are unable to help with)?

Answer 21

Editors help the readability of code

They are unable to help identify errors

Question 22

What is a runtime environment?

Answer 22

A runtime environment (RTE) is special software that allows a program to run on a computer, even if it is not designed to run on it

Question 23

What debugging tools exist to locate and fix errors?

Answer 23

Breakpoints (pause / stop code to check)

Variable tracing (identify changing variable values)

Syntax error pinpoint (error trapping)

Question 24

What is the purpose of defensive design?

Answer 24

To ensure that a program runs correctly and continues to run no matter what actions a user takes

Question 25

List some defensive design considerations

Answer 25

Protection against unexpected user inputs or actions, such as a user entering a letter where a number was expected

Maintainability - ensuring code is readable and understandable

Minimising / removing bugs

Question 26

What is validation?

Give some examples

Answer 26

Validation applies rules to inputted data, rejecting it if it doesn’t follow the rules

E.g. range check, length check, presence check, format check, type check etc…

Question 27

What is data sanitisation?

Answer 27

Hide / protect data so it cannot be seen or disclosed

E.g. masking hides visible data (password entry becomes *****)

Question 28

What is authentication?

Answer 28

Authentication is the process of a user confirming that they are who they say they are on a computer system

Question 29

What are the three authentication groups?

Answer 29

Something you are - username, bank account number, or anything that identifies the user uniquely

Something you know - password, pin, secret answer to a question

Something you have - swipe card, biometrics, any other physical identifying device

Question 30

What is the purpose of maintainability?

Answer 30

To ensure that, over time, a program can be maintained

Question 31

List how a program can be written in a maintainable style

Answer 31

Comments

Sensible variable names

Indentation

Question 32

What are the two types of programming error?

Answer 32

Syntax error

Logic error

Question 33

What is a syntax error?

Give some examples

Answer 33

A syntax error occurs when code written does not follow the rules of the programming language.

Misspelling a statement, e.g. writing pint instead of print
Using a variable before it has been declared
Missing brackets, e.g. opening a bracket but not closing it

Question 34

What is a logic error?

Answer 34

A logic error is an error in the way a program works. The program simply does not do what it is expected to do (usually the program continues to run).

Question 35

Give some examples of a logic error

Answer 35

Incorrectly using logical operators, e.g. expecting a program to stop when the value of a variable reaches 5, but using <5 instead of <=5

Incorrectly using Boolean operators

Unintentionally creating a situation where an infinite loop may occur

Incorrectly using brackets in calculations

Unintentionally using the same variable name at different points in the program for different purposes

Referring to an element in an array that falls outside of the scope of the array

Question 36

What is the difference between iterative testing and final (terminal) testing?

Answer 36

Iterative testing – carried out why a program is being being developed

Final (terminal) testing – carried out when all modules are complete and the program is tested as a whole

Question 37

What should test data include?

Answer 37

Valid data - sensible, possible data that the program should accept and be able to process

Extreme data - valid data that falls at the boundary of any possible ranges

Invalid (erroneous) data - data that the program cannot process and should not accept

Question 38

What should a good testing plan include?

Answer 38

The test number

A description of what the test intends to check

The test data being used

The type of test (valid, extreme or invalid)

Expected outcome

Actual outcome

Question 39

What is a trace table? Complete one for the following code (adding the integers 5, 7 and 9 to make 21)

Answer 39

Trace tables contain all the variable a program contains (and when their value changes, the table indicates this)

Question 40

What can potentially happen if programs aren’t tested fully?

Answer 40

Bugs