Algorithms - Pseudocode

Jamie Z 2024-02-05

Learning Goals

I am able to understand algorithm constructs
I am a able to communicating using Pseudocode

What are Algorithm Constructs?

There are basic building blocks that an algorithm consists of. Each of them serve a particular purpose

Sequence
Assignment - Assigning a value to a variable
Selection and Condition - If and else if statements
Iteration - Repeat a block of code
Modularization - Never write the same code again and again

What is Pseudocode

Pseudocode will be used as the formal method of symbolizing algorithms

Pseudocode can be used for

Demonstrating thinking that later can become comments in the final program
Describing how an algorithm should work
Explaining a computing process to less technical people
Generating code in collaboration with others.

Pseudocode does not have a standard format and varies from programmer to programmer. However, a number of conventions are generally used. QCAA has mandated certain conventions.

**Key words**

IF, THEN, ELSE ENDIF OUTPUT INPUT FOR LOOP END FOR WHILE LOOP END WHILE CALCULATE EQUAL TO GREATER THAN GREATER THAN AND EQUAL TO SET DECLARE TO THEN LESS THAN EQUAL TO

# Sequence

A sequence is a number of instructions that are processed one after the other.
For example, a very simple algorithm for brushing teeth might consist of these steps:
Each step is an instruction to be performed. Sequencing is the order in which the steps are carried out.

DECLARE count

SET count TO 1

OUTPUT the value of count

Why is sequencing important?

It is crucial that the steps in an algorithm are performed in the right order - otherwise the algorithm will not work correctly.

Example

Grab the bowl
Get cereal box from cupboard
Pour cereal out of box in the bowl
Obtain the milk bottle from the fridge
Pour milk into the bowl

Assignment

Assignment is used to store the value of an expression into a variable.
They are similar to the variables that you would have seen in maths e.g. x=5.
In programming, this is exactly the same idea, except computers can remember anything not just numbers, and additionally, the variables are generally given more meaningful names that relate to the data they contain e.g. Name = "Tom".
Assignment is the way that a variable is told to remember a certain value.

DECLARE studentname

SET studentname TO Bob

Selection and Condition

A selection statement uses a condition to select, or determine, the next line of the program that is to be executed.
These statements help to make decisions and change the flow of a program. In many languages, there are three types of selection statements:

IF Statement

The 'if' statement is one of the most basic and simplest controls flow statements. We can use the ‘if’ statement when we want to execute a group of one or more script statements only when a particular condition is met.

IF ELSE Statement

As we know, the ‘if’ statement allows us to execute a set of statements only when a particular condition is true. However, if we want to execute another set of statements when the condition is false, then we can use the ‘if....else’ statement.

CALCULATE totalCost

IF (totalCost > \(10) \)THEN

OUTPUT ‘no delivery charge’

ELSE

OUTPUT ‘\(5 delivery charge’\)

ENDIF

OUTPUT ‘thankyou’

Iteration

Iteration is also called repetition and is used when something is repeated over and over again, so anything where the program goes round in a loop
A FOR loop is used when it is known exactly how many times to go round the loop
A WHILE loop is used to repeat while a condition is true or false

Modularisation

Modularisation is used to reduce the complexity of a system by deconstructing it into more or less independent units or modules. We are going to use the term "function" as that is what they are called in most of the predominant programming languages of today. Functions are important because they allow us to take large complicated programs and to divide them into smaller manageable pieces and more easily maintained.

FUNCTION delivery_charge