1. Algorithms and Flowcharts

2. Activity 1 What is this an example of and why are they important?
It is of course a recipe
Important as it allows the same meal to be made, consistently, time and time again.
It outlines a set of steps to follow so that anyone can create the same result.

3. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Hands up if you can explain the following:
What is an algorithm?

4. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Algorithms
In general, an 'algorithm' is the name given to a set of steps needed to complete a task.
Think of an algorithm as a recipe.
For instance you could define an algorithm to make a cup of tea. You start by filling the kettle, then place a tea bag in the cup and so on.
In computer terms, an algorithm describes the set of steps needed to carry out a software task or solve a problem

5. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Algorithms
Writing algorithms is all about problem solving.
After being given a problem to solve, programmers never begin programming straight away, they will first do the following:
Think about the problem
Break the problem down into smaller chunks
Think of the steps needed to solve each chunk
Write down the steps – which in turn becomes the algorithm.
This is known as a top down design

6. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Writing Algorithms
Problem
Algorithm
Algorithms are independent of any language

7. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Hands up if you can explain the following:
What is an algorithm?

8. Activity 2
In your own words, write down the steps needed to solve the following problem.
“Create a program that inputs two numbers, adds them together and then outputs the result onto the screen.”

9. Activity 2 What did you get? Did you have something like this?…
Ask user for a number
Store it in variable “number1”
Ask user for a second number
Store this in variable “number 2”
Add the two numbers together
Store the result in variable “answer”
Display the contents of “answer”.

10. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Writing Algorithms
Writing an algorithm in a specific language:
Too time consuming
Pointless – could just code
Can’t be taken by a programmer using a different language
Too complex – need knowledge of syntax (code specific to a language)
Writing an algorithm in everyday language:
Too time consuming
Inaccurate as it could be open to interpretation
Algorithms are independent of any language
There are therefore methods used to write algorithms so that they are succinct, accurate and easy to understand so that a programmer of any language could understand the steps required to solve a task:
Flowcharts and Pseudocode

11. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Writing Algorithms
Problem: Calculate the Sales Tax (VAT) of an item and then using it to work out the final price
1. Flowchart
2. Pseudocode
Examples of each method of algorithm writing

12. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Flowcharts
Today we will focus on Flowcharts
Visual representation of a system
Small number of symbols used to represent individual steps
Arrows show the flow of control within the algorithm (the order of instructions)
Easier to trace a sequence of steps and locate errors than in pseudocode.
Start
Is temp < 19
Is temp > 21
Turn heating on
Turn heating off
Yes No
Example:
A central heating system will try to keep the temperature between 2 values (19 and 21)
If the temperature falls below 19 It will turn the heating system on
If the temperature rises above 21 it will switch the heating system off.

13. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Start and Stop Symbols
All flow charts begin with a Start Symbol and at the end of the flow chart (or at various end points of the chart) we place a Stop Symbol.
There are drawn as a rectangle with curved ends
Flowcharts and their symbols
Start
Stop

14. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Process Symbols
Most of the time a flow chart will demonstrate the sequence of instructions to be carried out.
Simple processes (like “Add 1 to x” or “append x to List”) are shown using a standard rectangle.
Flowcharts and their symbols
Add 1 to x
Append x to “List”

15. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Input / Output Symbols
At times your program will most certainly ask the user for inputs and output values too.
Inputs and Outputs (like “Name?” or “…display age”) are shown using a parallelogram.
Name?
Flowcharts and their symbols
Store in variable “Name”
Display Name

16. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Decision Symbols
At times your program will be programmed to make a decision based on certain conditions.
Decisions (like “IF X = 3” or “While Y > 3”) are shown using a diamond.
Flowcharts and their symbols
If X = 3
Yes
Display “X equals 3” No
Display “X doesn’t equal 3”

17. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Flowcharts and their symbols

18. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Flowcharts and their symbols

19. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
4 things you need to be able to do with algorithms for your exam
Understand them
Correct them if they have errors,
Complete them if they are incomplete
Produce them after being given a problem to solve

20. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Tips on reading algorithms.
Start from top and follow the arrows
Remember what the symbols mean
Read each symbol description
Logically work out what the algorithms is doing.
Task: What is this algorithm doing?

21. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Tips on correcting algorithms.
Start
Is temp > 19
Is temp < 21
Turn heating on
Turn heating off
Yes No
Read the flowchart and look for decisions which don’t make sense
Start
X = 10
while X < 10
Yes
X = X + 1
Or it might be a loop which you cannot get into or perhaps out of. No
End

22. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Tips on completing algorithms.
Start from top and follow the arrows
Remember what the symbols mean
Read each symbol description
Logically work out what the algorithms is doing.
THEN,
Use your knowledge of the algorithm so far
AND Use your knowledge of the follow chart symbols
…and complete the flowchart

23. Algorithms and Flowcharts
Learning Objectives:
(a) understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them
(b) produce algorithms in pseudocode or flow diagrams to solve problems.
Tips on writing algorithms.

24. Activity 3
Make notes explaining what an algorithm is, what a flowchart is and the flowchart symbols for:
start / stop
input / output
processes
Decisions