1.1 Algorithms

Question 1

What does ‘unambiguous’ mean?

Answer 1

It means that the instructions cannot be misunderstood.
Simply saying “turn” would be ambiguous because you can turn either left or right.
All instruction given on a computer must be unambiguous, otherwise, it would not know what to do.

Question 2

What is a ‘sequence’?

Answer 2

It is an ordered set of instructions.

Question 3

What is an ‘algorithm’?

Answer 3

It is a precise method for solving a problem.

Question 4

What is ‘High-level programming language’?

Answer 4

It is a programming language that resembles natural human language.

Question 5

What is a ‘flowchart’?

Answer 5

It is a graphical representation of an algorithm.
Each of the steps in the algorithm is represented by a symbol. Symbols are linked together with arrows showing the order in which steps are executed.

Question 6

What is a ‘pseudo-code’?

Answer 6

It is a structured, code-like language that can be used to describe an algorithm.

Question 7

What is a ‘variable’?

Answer 7

It is a ‘container’ used to store data.
The data stored in a variable is referred to as a value.
The value stored in a variable in not fixed. The same variable can store different values during the course of a program and each time a program is run.

Question 8

What is an ‘identifier’?

Answer 8

It is a unique name given to a variable or a constant. Using descriptive names for variables makes code much easier to read.

Question 9

What is an ‘arithmetic operator’?

Answer 9

It is an operator that performs a calculation on two numbers.

Question 10

What is a ‘constant’?

Answer 10

It is a ‘container’ that holds a value that never changes.

Like variables, constants have unique identifiers.

Question 11

Construct

Answer 11

A component from which something is built.

Letters and numbers are the constructs we use to build our own language and convey meaning.

Question 12

Selection

Answer 12

A construct that allows a choice to be made between different alternatives.

Question 13

Iteration

Answer 13

A construct that means the repetition of a process.

An action is repeated until there is a desired outcome or a condition is met. It is often referred to as a loop.

Question 14

IF…THEN…ELSE statement

Answer 14

This statement allows a choice to be made between 2 alternatives based on whether or not a condition is met.

Question 15

Relational operator

Answer 15

An operator that compares 2 values.

Question 16

Nested IF statement

Answer 16

It consists of one or more IF statements placed inside each other. A nested IF is used where there are more than 2 possible courses of action.

Question 17

Indefinite iteration

Answer 17

This is used when the number of iterations is not known before the loop is started. The iterations stop when a specified condition is met.
This sort of loop is said to be condition controlled.

Question 18

Definite iteration

Answer 18

This is used when the number of iterations, or turns of the loop, is known in advance. It can be sent as many times as you want. This sort of loop is said to be count controlled.

Question 19

Logical Operator

Answer 19

A Boolean operator using AND, OR and NOT.

Question 20

Random number

Answer 20

A number within a given range of numbers that is generated in such a way that each number in the range has an equal probability of occurring.
There are many devices for generating n=random numbers. For example in Excel, it has a built-in RANDOM command: RANDOM(uppperLimit)

Question 21

Nested loop

Answer 21

A loop that runs inside another loop. The inner one executes all of its instructions for each turn of the outerloop.

Question 22

Concatenation

Answer 22

The linking together of 2 or more items of information.

Question 23

Logic error

Answer 23

An error in an algorithm that results in incorrect or unexpected behavior.

Question 24

Trace table

Answer 24

A technique used to identify any logic errors in algorithms. Each column represents a variable or output and each row a value of that variable.

Question 25

Simulation

Answer 25

A representation of a real world process or system.

Question 26

Array

Answer 26

An organised collection of related values that share a single identifier.

Question 27

Traversal

Answer 27

Travel across or through something. An array can be traversed by moving from the first to the last element in order to examine the data stored at each index position.

Question 28

Recursion

Answer 28

A process that is repeated. For example, a document can be checked and edited, checked and edited and so on until it is perfect.

Question 29

Brute force

Answer 29

An algorithm design that does not include any techniques to improve performance, but instead relies on sheer computing power to try all possibilities until the solution to a problem is found.

Question 30

Divide and conquer

Answer 30

An algorithm design that works by dividing a problem into smaller sub-problems, until they are easy to solve. The solutions to these are then combined to give a solution to the complete problem.

Question 31

Median

Answer 31

The middle number when numbers are ordered in ascending or descending order.