Teaching Computing…
…to GCSE Level with Python
Sue Sentance
Sue.sentance@anglia.ac.uk
Course overview
Week No Date
Computing Theory
(5:30 – 6:30)
1
15/01/2013
Structure of the course
Introduction to Binary
2
3
4
5
22/01/2013
29/01/2013
05/02/2013
12/02/2013
(start 6pm)
26/02/2013
05/03/2013
(start 6pm)
12/03/2013
19/03/2013
26/03/2013
More binary logic/hex
Truth tables/logic diagrams
Structure of the processor
Algorithms and Dry Runs
Variables/assignme
nt
Selection
Iteration
Iteration/Lists
More on lists
The internet
Networking/ HTML and CSS
Functions
Files
Database theory
GCSE Controlled Assessment Tasks
GCSE Controlled Assessment Tasks
Databases
Databases
Consolidation
6
7
8
9
10
Programming in
Python
(6:30 – 8:00)
Available specifications for
2012-2013
 OCR – will be in third year
 EdExcel – now delayed until September 2013
 AQA – up and running from September 2012
 Behind the Screen – E-Skills work-in-progress to create a
GCSE in Computer Science
OCR GCSE Computing
3 units
A451 – Theory (Examination)
A452 – Practical investigation (Controlled Assessment)
A453 – Programming (Controlled Assignment)
AQA Computer Science
 Component 1 – Practical programming
50 hours controlled assessment
Worth 60%
 Component 2 – Computing fundamentals
1 ½ hour examination
Worth 40%
Today’s session
4:45 – 5:45 Binary & Binary arithmetic/ Hex
6.00 – 7.30 Starting to program in Python
From the specification
OCR
AQA

(a) define the terms bit, nibble, byte, kilobyte,
megabyte, gigabyte, terabyte

understand that computers use the binary
alphabet to represent all data and instructions

(b) understand that data needs to be converted into a
binary format to be pro

understand the terms bit, nibble, byte, kilobyte,
megabyte gigabyte and terabyte

(c) convert positive denary whole numbers (0-255) into
8-bit binary numbers and vice versa

understand that a binary code could represent
different types of data such as text, image, sound,
integer, date, real number

(d) add two 8-bit binary integers and explain overflow
errors which may occur

understand how binary can be used to represent
positive whole numbers (up to 255)

(e) convert positive denary whole numbers (0-255) into
2-digit hexadecim

understand how sound and bitmap images can
be represented in binary

understand how characters are represented in
binary and be familiar with ASCII and its limitations

understand why hexadecimal number
representation is often used and know how to
convert between binary, denary and hexadecimal
Binary numbers
0
Binary numbers
1
Learning binary numbers
 Converting binary to denary
 Converting denary to binary
 Binary addition
Storing Binary Numbers
Inside the computer each binary digit is stored
in a unit called a bit.
A series of 8 bits is called a byte.
A bit can take the values 0 and 1
What is meant by?
1 byte ?
1 nibble ?
1 kilobyte ?
1 megabyte ?
1 gigabyte ?
1 terabyte ?
Storing data
1 byte = 8 bits
1 nibble = 4 bits
1 kilobyte = 1024 bytes = 2 10 bytes
1 megabyte = 2 20 bytes = 210 kilobytes
1 gigabyte = 2 30 bytes = 210 megabytes
1 terabyte = 2 40 bytes = 2 10 gigabytes
Activity
Binary counting exercise
How to convert Binary
Numbers to denary
Place
values 128 64 32 16 8
1
0
0
1
1
4
2
1
0
1
1
128+0+0+16+8+ 0+ 2 +1 = 155
in Denary
Storing Numbers - Binary
EXAMPLE
Convert the binary number
1011 0111 into denary:
Answer
128 64 32 16 8
1 0 1 1 0
=128+32+16+4+2+1=183
4
1
2
1
1
1
Conversion Exercise
Convert the following binary numbers into denary:
001
010
1000
1001
101
110
1010
1111
1100
10101
10111
11111
Teaching binary
 Holding cards up activity
 Finger binary
 Cisco binary game
 CS Unplugged actitivies
Converting Denary to Binary
 Write down the column headings for the binary number:
64
32
16
8
4
2
1
 Process each column from left to right.
 If the denary number to be translated is greater than or
equal to the column heading, place a 1 in the column and
subtract the value of the column from the denary value.
 If the denary value is smaller than the column heading,
place a 0 in the column.
Convert to Binary
3
5
8
7
11
16
32
21
14
17
48
255
Sizes of Binary Numbers
 If we have 4 bits available the largest number is
1 1 1 1 (which is 15 in denary)
 If we have 5 bits available the largest number is
1 1 1 1 1 (denary value 31)
 If we have 7 bits available the largest number is
1 1 1 1 1 1 1 (denary value 127)
 If we have 8 bits available the largest number is
1 1 1 1 1 1 1 1 (denary value 255)
 Can you see a pattern?
animated
To calculate the max size
 In general if we have n bits available then the
largest denary number we can store is
n
2 -1
 For example, for 3 bits, 1112 = 23 – 1 = 8 – 1 = 7
Addition Rules for Binary
0+0=0
1+0=1
0+1=1
1 + 1 = 10 (write down 0 and carry 1)
1 + 1 + 1 = 11 (write down 1 and carry 1)
Adding Binary Numbers
add 8 and 5
8
1000
5
0101
---------------13
1101
check the answer using place values:
8+4+0+1 = 13
Adding Binary Numbers
add 9 and 5
9
1001
5
0101
1
---------------14
1110
carry
check the answer using place values:
8+4+2+0 = 14
Exercises – see sheet