Learning Objectives:
 Convert positive denary integers (0‐255) into 2‐digit hexadecimal numbers and vice versa
 Convert between binary and hexadecimal equivalents of the same number
 Explain the use of hexadecimal numbers to represent binary numbers
Suggested time: 50 mins
Starter:
I started by showing two numbers on the board (one in binary and one in hex).
1101 1001
C9
I then asked the students, “Which is easiest to remember?”
I explained to students that we often find it difficult to remember long sequences of numbers so, to make life easier, we can break the number down from 4 bits (a nibble) to 1bit.
Demonstration (Hexadecimal):
Next, I explained that the smallest value we can have in 4bits (nibble) is 0000 (0 in denary) and the largest value is 1111 (15 in denary) and that we needed to represent each value with a single digit. I then displayed the following table on the whiteboard and asked students to fill in boxes 09:
Denary  0  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15 

















I then asked the students to suggest ways we would represent the last 6 numbers without using numbers.
I then explained that, to get around this problem, we substitute the numbers 10 to 15 with the letters A to F. I explained that we call this system Hexadecimal (or Hex for short). I followed this by showing the students the following table:
Denary  0  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15 
Hex  0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F 
Denary  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31 
Hex  10  11  12  13  14  15  16  17  18  19  1A  1B  1C  1D  1E  1F 
Next, I split the class into groups of three and gave each group a copy of the following table. I then asked them to fill in the blanks:
Denary  48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63 
Hex 
















starter.pdf 
Hex  Denary (Decimal) 
0F  15 
10  16 (1x16) 
20  32 (2x16) 
30  48 (3x16) 
40  64 (4x16) 
50  80 (5x16) 
60  96 (6x16) 
70  112 (7x16) 
80  128 (8x16) 
90  144 (9x16) 
A0  160 (10x16) 
Activity 1 (Denary <> Hex):
Next I explained that, for the exam, students are expected to be able to convert binary to hexadecimal.
I then showed the students the following video:
(a) Convert the hexadecimal number 6A to denary. (You must show your working out).
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............................................................................................................................ (2)
I followed this by giving students a series of mini challenges (See answer sheet at bottom of this page):
activity_1.pdf 
Activity 2 (Binary <> Hex):
Finally I explained that, also for the exam, students are expected to be able to convert binary to hexadecimal.
I explained that, in the exam, students are expected to be able to convert 8bit binary numbers to hex. I then demonstrated how to do this using the following example:
bin2hex.pdf 
(a) Convert the binary number 00111101 to hexadecimal.
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............................................................................................................................ (2)
I finished by putting this all into context. I displayed the following table on the board and asked students if they recognised it. I then asked if they spotted anything familiar (based on the lesson).
Homework:
Students were instructed to update their class revision wiki.
Denary  48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63 
Hex  30  31  32  33  34  35  36  37  38  39  3A  3B  3C  3D  3E  3F 
activity_1_answers.pdf 
Useful Links:
Suggested time: 50 mins
Main:
Students were instructed to setup their Raspberry Pis and to launch IDLE 3.
Students were then asked to follow 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.