
Learning Objectives:
- Explain the use of binary codes to represent characters
- Explain the term character set
- Describe with examples (for example ASCII and Unicode) the relationship between the number of bits per character in a character set and the number of characters which can be represented
Suggested time: 50 mins
Starter:
Students were given the following worksheet and asked to complete the tasks:

starter.pdf |
I explained that, in the previous lesson, we have looked at how numbers are represented in a computer using binary. I then explained that characters are converted in the same way using something called a character set.
Next, I explained that one of the most commonly used character sets is ascii (American Standard Code for Information Interchange). I then showed students the full 7-bit ascii table (See below).

7-bit_ascii_table.pdf |
Finally, I gave students each a worksheet containing part of the ascii table (containing the letters A to Z in uppercase and lowercase) and asked the students to fill in the gaps in the table. Once complete, I asked the students to attempt the challenges on the worksheet (see below)

ascii_secret_agent_challenge.pdf |

ascii_secret_agent_challenge_answers.pdf |
Representation of text - http://web.eecs.utk.edu/research/cs100modules/module3/index.html
Ascii text to Binary converter - http://www.binaryhexconverter.com/ascii-text-to-binary-converter
Ascii Binary conversion chart - http://www.nthelp.com/ascii.htm
Text to Ascii and Binary converter - http://www.computingacademy.org.uk/text-ascii-and-binary-converter
Suggested time: 50 mins
Main:
Students were instructed to setup their Raspberry Pis and to launch IDLE 3.
Students were then asked to continue to work through Mark Clarckson’s Introduction to Python booklet: (http://community.computingatschool.org.uk/resources/14)
Alternative:
Alternatively, if you do not have access to a set of Raspberry Pis, students can still complete the Python challenges:
To install Python for FREE, go to the python.org website and download a standard installation of the latest version of Python. This will provide you with everything you need.