1. 3.1 Fundamentals of algorithms
3.1.1 Representing algorithms (pseudo-code)
Lesson

2. What do these words mean to you?
Code
Ambiguous
Pseudo
What do these words mean to you?
Flowchart
Decomposition
This slide is designed as a starting point to find a baseline of understanding.

3. Objectives 1. Know what pseudo-code is.
2. Understand the link between code, pseudo-code and flowcharts.
3. Understand the main pseudo-code methodologies.
4. Be able to solve a problem using pseudo-code.
Keywords:
Pseudo-code Flowchart
Code Problem Solution
Whilst this lesson is focussed on pseudo-code, the link between code and flowcharts needs to be borne in mind.

4. Flowcharts provide an overview of how to solve a problem.
1. Know what pseudo-code is.
2. Understand the link between code, pseudo-code and flowcharts.
Pseudo-code looks at in-depth algorithms to solve problems without having to worry about code syntax.
Pseudo-code is almost computer code – but not quite. Think of it as a half-way house between a flowchart overview and actual computer code.
Computer code implements algorithms in such a way that a computer can understand it.
Students need to understand that pseudo-code is a means to an end. In this presentation we look at one approach and form a link between flowcharts, pseudo-code and code. This is the format that students will be presented with in exams. When writing their own code it just has to be understandable and unambiguous.

5. Contents Sequence Variable assignment If...Then If...Then... Else Case
While loops
Repeat loops
For loops
Procedures
Procedures with parameters
Functions
Each of the above is a hyperlink which will take you to the relevant section in the presentation.
Each section consists of an explanation of the word or phrase, a task and a blank slide for students’ responses.
Writing files
Reading files

6. Sequence 3. Understand the main pseudo-code methodologies.
x  USERINPUT
OUTPUT x
The left arrow indicates assignment.
The user input is put in to x.
Programs have to flow in sequence. You can’t divide a total by the number of elements to work out an average if you haven’t added them up first. It is expected that teachers talk through the pseudo-code – this is not a topic that you can just look at!
There is often a 1-to-1 relationship between pseudo-code and actual code.
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7. Task: Write pseudo-code to input your name
4. Be able to solve a problem using pseudo-code.
Sequence
Task: Write pseudo-code to input your name
and age and output them to the screen.
Allow 3-4 minutes.
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8. Sequence 4. Be able to solve a problem using pseudo-code
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
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9. gridOfWords[3][4]= ”hello”
3. Understand the main pseudo-code methodologies
Variable assignment
The left arrow indicates assignment
singleNumber3
listOfNumber[3]5
gridOfWords[3][4]”hello”
initialisedList[2, 32, 45, -1]
singleNumber3
listOfNumber[3]5
gridOfWords[3][4]”hello”
initialisedList[2, 32, 45, -1]
singleNumber = 3
listOfNumber[3] = 5
gridOfWords[3][4]= ”hello”
initialisedList = [2, 32, 45, -1]
Arrays or lists use square brackets to identify elements within them
These are examples of assignation, this is not a full program.
Lists can be initialised with values
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10. Task: Create pseudo-code to create a list of exam results.
4. Be able to solve a problem using pseudo-code.
Variable assignment
Task: Create pseudo-code to create a list of exam results.
Extension: Create a list of names that link to the exam results.
Allow 3-4 minutes.
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11. Variable assignment 4. Be able to solve a problem using pseudo-code
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
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12. If ... then 3. Understand the main pseudo-code methodologies.
Text has speech marks around it.
Comparisons are common sense.
Discussions can cover use of single/double speech marks for strings, comparison operators.
Control statements have an END <statement> to aid understanding.
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13. 4. Be able to solve a problem using pseudo-code.
If…then
Task: Create pseudo-code to input an exam grade and output a message to the screen if it is a pass grade.
Allow 3-4 minutes.
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14. If … then 4. Be able to solve a problem using pseudo-code.
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
Back to Contents

15. Control statements have an END <statement> to aid understanding.
3. Understand the main pseudo-code methodologies.
If … then ... else
Note the end is still ENDIF and after the else.
Control statements have an END <statement> to aid understanding.
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16. 4. Be able to solve a problem using pseudo-code.
If … then ... else
Task: Extend your previous pseudo-code to output a different message if it is a fail grade.
Allow 2-3 minutes.
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17. If ... then ... else 4. Be able to solve a problem using pseudo-code.
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
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18. Control statements have an END <statement> to aid understanding.
3. Understand the main pseudo-code methodologies.
Case
In the case of x being…
Discussion as to simplicity of multiple tests as opposed to nested decisions.
Control statements have an END <statement> to aid understanding.
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19. 4. Be able to solve a problem using pseudo-code.
Case
Task: Create pseudo-code to output a different message for each exam grade that can be entered.
Allow 4-5 minutes.
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20. Case 4. Be able to solve a problem using pseudo-code. Back to Contents
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
Back to Contents

21. While loops 3. Understand the main pseudo-code methodologies.
Criteria is the same for coding, flowcharts and pseudo-code.
Discussion as to criteria, choice of type of loop.
Control statements have an END <statement> to aid understanding.
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22. 4. Be able to solve a problem using pseudo-code.
While loops
Task: Create pseudo-code to repeatedly input a number and add it on to a total until they input a number which is less than 0
Allow 5-6 minutes.
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23. While loops 4. Be able to solve a problem using pseudo-code.
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
Back to Contents

24. Criteria is the same for coding, flowcharts and pseudo-code.
3. Understand the main pseudo-code methodologies.
Repeat loops
Criteria is the same for coding, flowcharts and pseudo-code.
Discussion as to choice of loop. Counting loop = FOR, at least once = REPEAT, may not be needed at all = WHILE. Pyhon does not have a REPEAT loop so a cheat is needed.
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25. 4. Be able to solve a problem using pseudo-code.
Repeat loops
Task: Create pseudo-code to initialise a variable by 2 and then repeatedly output the variable and then times it by itself until the variable exceeds 1,000,000
Allow 5-6 minutes.
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26. Repeat loops 4. Be able to solve a problem using pseudo-code
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
Back to Contents

27. For loops 3. Understand the main pseudo-code methodologies.
For loops need ranges to loop through.
FOR loops are for counting loops.
Control statements have an END <statement> to aid understanding.
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28. 4. Be able to solve a problem using pseudo-code
For loops
Task: Create pseudo-code to fill a list with ten names, and then use a ‘For’ loop to output them one at a time.
Allow 4-5 minutes.
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29. For loops 4. Be able to solve a problem using pseudo-code.
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
Back to Contents

30. Procedures 3. Understand the main pseudo-code methodologies.
You have to differentiate between procedures and functions.
Control structures have an END <statement> to aid understanding.
Procedures without parameters are useful for taking long and distracting elements of code (such as outputting menus and large amounts of text) outside of the main program flow.
Call procedures by name.
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31. 4. Be able to solve a problem using pseudo-code.
Procedures
Task: Create a pseudo-code procedure that outputs your name five times. Call the procedure by name.
Allow 3-4 minutes.
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32. Procedures 4. Be able to solve a problem using pseudo-code.
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
Back to Contents

33. Procedures with parameters
3. Understand the main pseudo-code methodologies.
Parameters are passed in with a name.
Control structures have an END <statement> to aid understanding.
Procedures with parameters allow pieces of code to be repeated with some variation
Call procedures by name and include a value or variable as the parameter.
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34. Procedures with parameters
4. Be able to solve a problem using pseudo-code.
Task: Adapt your previous procedure to accept a name as a parameter and output it five times.
Extension: Accept a second parameter to specify the number of times to repeat the name.
Allow 4-5 minutes.
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35. Procedures with parameters
4. Be able to solve a problem using pseudo-code.
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
Back to Contents

36. Functions 3. Understand the main pseudo-code methodologies.
Parameters are passed in with a name.
The result of the calculation is returned.
Functions can be used to produce repeated mathematical calculations amongst many other things.
The returned value is assigned to a variable for use.
Call functions by name and include a value or variable as the parameter.
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37. 4. Be able to solve a problem using pseudo-code.
Functions
Task: Create pseudo-code to create a function that accepts a number as a parameter, and then adds a random number between 1 and 10 to the number and returns the answer.
Allow 4-5 minutes.
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38. Functions 3. Understand the main pseudo-code methodologies.
Parameters are passed in with a name.
The result of the calculation is returned.
Functions can be used to produce repeated mathematical calculations amongst many other things.
The returned value is assigned to a variable for use.
Call functions by name and include a value or variable as the parameter.
Back to Contents

39. Writing files 3. Understand the main pseudo-code methodologies.
LEN is a function for getting the size of a file or list.
Lists start at 0 but AQA pseudo-code files start at 1
Python has easier to use in-built functions – pseudo-code should be independent of a programming language.
Writing text files in AQA pseudo-code is contrary to most programing languages. It is important that students remember that as long as their code is clear and unambiguous then they will be fine.
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40. Extension: Repeat forever until the user inputs the word “stop”.
4. Be able to solve a problem using pseudo-code.
Writing files
Task: Create pseudo-code to ask for a word and write it to a file. This should be repeated five times.
Extension: Repeat forever until the user inputs the word “stop”.
Allow 4-5 minutes.
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41. Writing files 4. Be able to solve a problem using pseudo-code.
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
Back to Contents

42. Reading files 3. Understand the main pseudo-code methodologies.
LEN is a function for getting the size of a file or list.
AQA suggest pseudo-code that reads a line at a time
Python has easier to use in-built functions – pseudo-code should be independent of a programming language.
Reading text files in AQA pseudo-code is contrary to most programing languages. It is important that students remember that as long as their code is clear and unambiguous then they will be fine.
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43. Extension: Extend the pseudo-code to output the file in reverse order.
4. Be able to solve a problem using pseudo-code.
Reading files
Task: Create pseudo-code to read in the file you created in the last task and output it to screen.
Extension: Extend the pseudo-code to output the file in reverse order.
Allow 4-5 minutes.
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44. Reading files 4. Be able to solve a problem using pseudo-code.
This slide is an opportunity for students to use an interactive whiteboard to write up their pseudo-code. The whole group can then discuss, look at alternatives, identify areas which are different from AQA pseudo-code and whether they are acceptable or not.
Back to Contents

45. 1. Know what pseudo-code is.
2. Understand the link between code, pseudo-code and flowcharts.
3. Understand the main pseudo-code methodologies.
4. Be able to solve a problem using pseudo-code.
Complete the following tasks:
Review the flowcharts you have created for your controlled assessment.
Take one subroutine at a time and create pseudo-code to form an algorithm.
Remember:
Pseudo-code should be independent of the programming language.
Pseudo-code should be clear.
Pseudo-code should be unambiguous.
These are quite challenging, it may be worth doing this (and the previous requirement of creating flowcharts) on a previous controlled assessment prior to trying with the real ones.