Visual to text coding
Lesson 7: Times table

Years 5-6; 7-8

This is the seventh in a series of lessons to transition from visual coding to text-based coding with a General Purpose Programming language.

Included videos can be used by a teacher and/or students to see how to code each of the simple programs step-by-step in all three languages: Scratch, Python and JavaScript.

This lesson may take two to three 45-minute periods. It introduces iteration (also called loops).

Links with Digital Technologies Curriculum Area
Strand	Year	Content Description
Processes and Production Skills	5-6	Design, modify and follow simple algorithms involving sequences of steps, branching, and iteration (repetition) (ACTDIP019)
Processes and Production Skills	7-8	Design algorithms represented diagrammatically and in English, and trace algorithms to predict output for a given input and to identify errors (ACTDIP029) Implement and modify programs with user interfaces involving branching, iteration and functions in general-purpose programming language (ACTDIP030)

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Learning hook

Let’s talk about strategies to win a game like noughts-and-crosses (tic-tac-toe), or to solve a puzzle like Sudoku. What is your strategy?

Do you take risks and make guesses?
Do you write down possibilities, trying to predict the future before making your move? If so, how many moves ahead can you predict?

In 1996, a supercomputer named Deep Blue won a chess game against Garry Kasparov, the reigning chess champion at the time.

As a class, discuss the question: Was Deep Blue smarter than Kasparov?

Some prompts to help in the discussion:

What sort of strategies might Deep Blue have used?
Thinking fast may not be the same as thinking smart.
With noughts-and-crosses, there’s a small number of ways the game can play out, enough for a human to know for certain the best move at any time. What makes chess different to noughts-and-crosses?
Computers, robots and other machines are great at repetitive tasks that bore or exhaust humans, known as iteration.

Deep Blue used a brute force method to win chess. It used its powerful processor to test out millions of possible futures in the game, over and over, then to select the move most likely to result in a win. Many times, computer programs seem ‘smart’, but they just have access to more data than a human and can repeat a behaviour more quickly.

Long Zheng/flickr, CC BY-SA 2.0

THOUGHT EXTENSION 1:

Could a powerful enough computer predict every single possible outcome of a chess game, guaranteeing that it would know how to win at every stage? This video on ‘Shannon’s number’ reveals there are more games of chess than you might ever imagine.

THOUGHT EXTENSION 2:

What other approaches are computer scientists taking to make computers smarter at chess?

Learning map and outcomes

In this lesson, students will:

access an online programming environment for visual code (Scratch) and for general-purpose programming (Python or JavaScript)
practise writing loops (iteration) in two forms – a while loop and a for loop
code a times table generator that produces a times table for any number that is entered.

Learning input

Begin by watching the following video introducing loops:

BEGIN
  For n from 1 to 5
    Display ‘DEFCON ’, n
  End For
END

PROGRAM OUTPUT:
DEFCON 1
DEFCON 2
DEFCON 3
DEFCON 4
DEFCON 5

BEGIN
  Repeat 4 times
    Display ‘May it rain,’
  End Repeat
  Display ‘Whisper words of water,    
may it rain.’
END

PROGRAM OUTPUT:
May it rain,
May it rain,
May it rain,
May it rain,
Whisper words of water, may it rain.

Now implement the two programs in Python or JavaScript, using the for loop techniques learned in the video.

Solution code:

Learning construction

For more on setting up and choosing a language, see Setting Up.

Step 1: Solution development

This video demonstrates coding the solution in Python and JavaScript. Try it yourself before checking the solution code.

Rules vs. conventions

By now, you have probably noticed that some coding ‘rules’ seem to matter more than others. Here are some examples of rules versus conventions:

Rule

(Do this or you will likely cause a syntax error or a bug in your program!)

Convention

(Do this for code readability, but some programmers may disagree.)

Use round brackets with display commands. For example:

Python: print("Hello")

JavaScript: document.write("Hello");

Use single quotes inside display commands. Double quotes also work. For example:

Python: print("Hello")

JavaScript: document.write("Hello");

In Python, indent code inside structures. For example

if (10 > 5):

print('Of course!')

In JavaScript, indenting is strongly recommended.

Indented:

if (10 > 5) {

document.write('Of course!');

}

Not indented:

if (10 > 5) {

document.write('Of course!');

}

In JavaScript, use var (or let) to declare variables.

(There is a subtle difference between var and let, important once you make complex programs. You can learn more here.)

Use ‘camel case’ for variable names. For example:

myName, orderTotal, noOfStars

Some Python coders prefer underscores:

my_name, order_total, no_of_stars

Use == for comparison of two numbers, never a single = sign. For example:

Python:

if (rating == 5):

print('5 stars!')

JavaScript:

if (rating == 5) {

document.write('5 stars!');

}

Include spaces in Maths statements.

Often, they’ll work without spaces. For example:

Python:

if ( rating==5):

print('5 stars!')

JavaScript:

if (rating==5) {

document.write('5 stars!');

}

As with spoken languages, some rules used to be universally accepted as strict, but now are sometimes ignored, such as using semicolons (;) at the end of code lines in JavaScript. Whether this will cause a syntax error may depend on the coding environment being used.

Finally, some conventions are just habits. For example, programmers often use the name i for the index variable in loops, because ‘i’ is short for ‘index’. But you could use another letter like n, or a word like index for the variable name.

Solution code:

Step 2: Tinker task

Modify your times table program to go all the way up to 20.

Next, add a second prompt to ask the user how high the times table should go. For example, if they enter 25, the times tables goes all the way up to 25.

Lastly, add a second table that shows the powers for the number. Here’s an example of the output:

5 to the power of 0 = 1

5 to the power of 1 = 5

5 to the power of 2 = 25

5 to the power of 3 = 125

...

You may need to research how to perform this operation in Python or JavaScript. Refer to the Resources for cheat sheets.

Solution code:

Challenge

These challenges use the skills covered so far. By writing or modifying their own programs, students have an opportunity to demonstrate Application and Creation.

1. Carefully examine the password check system in the flow chart below.

Image: Flow chart for password check system

a. Convert the algorithm to pseudocode (structured English) first. You will need to use a while loop to handle the repetition, so it won’t be the exact same sequence as the flowchart.

BEGIN
    password ← “x1yG2k4!”
    Display “Enter the password”
    guess ← input from user
    While guess is not equal to password repeat
        Display “Try again”
        guess ← input from user
    End While
    Display “Access Granted!”
END

b. Code the program in Python or JavaScript.

Solution code:

2. Improve the password check program in Challenge 1 so that there is a limited number of guesses before the program ends. HINT: You’ll need to add a variable to keep track of the number of tries.

Solution code:

3. (Optional) Create a countdown, rather than counting up. The output of the program should be:

	Beginning countdown
	10
	9
	8
	7
	6
	5
	4
	3
	2
	1
	Blast off!

There are at least two ways you can do this, as shown in these solution codes. One way does not require any new knowledge about loops.

Solution code:

4. (Optional) Choose from the links below to find pre-made code with some arrays declared. The code also includes a simple program to display all the items in the colours array using a loop.

Add some code to display all the items in the months array using a loop.

Finally, add some code to find the sum of all the items in the numbers array.

Solution code:

Resources

Setting up online environments
Online environments for coding in each language
- Scratch
- repl.it: an online environment suited to Python
- JSFiddle: an online environment suited to JavaScript
Cheat sheets listing basic commands for coding:
- Python Cheatsheet (from Grok Learning)
- JavaScript CheatSheet (Tip: Press the little blue tabs to move Variables, Basics, Strings and Data Types to the top.)

Previous lesson

Index page

Next lesson

Visual to text coding
Lesson 7: Times table

This is the seventh in a series of lessons to transition from visual coding to text-based coding with a General Purpose Programming language.

Included videos can be used by a teacher and/or students to see how to code each of the simple programs step-by-step in all three languages: Scratch, Python and JavaScript.

This lesson may take two to three 45-minute periods. It introduces iteration (also called loops).

Learning Sequence

Learning hook

THOUGHT EXTENSION 1:

THOUGHT EXTENSION 2:

Learning map and outcomes

Learning input

Two types of loops

Solution code:

Learning construction

Step 1: Solution development

Rules vs. conventions

Solution code:

Step 2: Tinker task

Solution code:

Challenge

Solution code:

Solution code:

Solution code:

Solution code:

Solution code:

Resources

Curriculum

Whole-school approaches

Lessons and ideas

Assessment

Inclusive curriculum

Professional learning

Technologies resourcing

Families

Related careers

Coding and games

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Visual to text codingLesson 7: Times table

This is the seventh in a series of lessons to transition from visual coding to text-based coding with a General Purpose Programming language.

Included videos can be used by a teacher and/or students to see how to code each of the simple programs step-by-step in all three languages: Scratch, Python and JavaScript.

This lesson may take two to three 45-minute periods. It introduces iteration (also called loops).

Learning Sequence

Learning hook

THOUGHT EXTENSION 1:

THOUGHT EXTENSION 2:

Learning map and outcomes

Learning input

Two types of loops

Two types of loops

The video on loops introduces two types of loops: while and for.

Solution code:

Learning construction

Step 1: Solution development

Rules vs. conventions

Rules vs. conventions

By now, you have probably noticed that some coding ‘rules’ seem to matter more than others. Here are some examples of rules versus conventions:

Solution code:

Step 2: Tinker task

Solution code:

Challenge

Solution code:

Solution code:

Solution code:

Solution code:

Solution code:

Resources

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Curriculum

Whole-school approaches

Lessons and ideas

Assessment

Inclusive curriculum

Professional learning

Technologies resourcing

Families

Related careers

Coding and games

MORE INFORMATION

Digital Technologies Hub is brought to you by

Visual to text coding
Lesson 7: Times table