Lesson 10: Simple functions

First, have students prepare their Internet browser to use Scratch along with an online environment for Python or an online environment for JavaScript. See the video above for how to access and test each of these environments. Note that this JavaScript environment does not work in Microsoft Edge (last tested February 2020).

Individually, practice writing a simple program in Scratch to draw the alphabet letters that make your initials, then code and test the same program in Python or JavaScript.

Notes:

• No need to create functions yet.
• Try to make your letters as accurate as possible, with the same height and appropriate width.
• It is easier at first to do straight lines than curves, so consider doing letters that are “blocky”.

Step 1: Function challenge in Scratch

The above video demonstrates a basic shape-drawing function in Scratch and ends with a challenge. Try it yourself before checking the conclusion of the video below.

Step 2: Function challenge in Python and Javascript

The above video shows how to implement STEP 1 in Python and JavaScript. Try it yourself.

Step 3: Function exercise with turtle graphics

Carefully read the pseudocode below.

1   BEGIN
2     Function drawHouse()
3       Forward 50
4       Left 90
5       Forward 50
6       Left 45
7       Forward 35
8       Left 90
9       Forward 35
10      Left 45
11      Forward 50
12      Left 90
13    EndFunction
14
15    Pen down
16    drawHouse()
17    Pen up
18    Forward 100
19    Pen down
20    drawHouse()
21  END

This program draws not one but _______ houses side by side. The main program begins at line number ____. After activating the pen, the program calls the ______________ function, which produces a shape. The function begins at line number ____ and ends at line number ____. Once the house shape is drawn, we return to the _______ __________. Next, the pen is ______________ and the turtle moves forward 100 units. Finally, the pen is reactivated and ______________ is called again.

STEP 4: Function exercise without turtle graphics

Carefully read the pseudocode below. This program does not use turtle graphics.

1   BEGIN
2     Function assignPasscode()
3       answer ← Input 'What is your name?'
4       Display 'Hi', answer, '. Here is your passcode:'
5       passcode ← Random number between 1000 and 9999
6       Display passcode
7     EndFunction
8
9     Repeat 4 times
10      Display 'Assigning a new passcode...'
11      assignPasscode()
12      Display ''
13    End Repeat
14  END

Now, fill in the missing words in the paragraph below, to explain what the program does.

This program assigns random passcodes for four people. The main program begins at line number ___. It contains a _______ which happens ___ times. Each time, it prints ‘Assigning a new passcode...’ and also ________ a function called assignPasscode(). The function asks the user for their ________. It then generates a passcode as a number between _______ and _______. This is displayed for the user.

1. Write and test a function to create a small star shape. In the same program, write and test another to create a big star shape. See the images below for sample shapes to aim for.
   With your functions created, use the main program to create a star-filled sky with a mix of large and small stars.
   Note: You may choose to use loops in the main program to help reduce repetition.
2. Write and test a function to create a small geometric shape. Use that function as part of a main program to create a geometric design. As a further challenge add colour to the design.
3. (Without turtle graphics) Choose a popular song with a few verses as well as a chorus that recurs. Write and test one function for each verse, as well as one function for the chorus. These functions should simply display the words.
   In the main program, call the verse and chorus functions in the correct order to display the complete song. You may need to call the chorus function more than once.