1. …to GCSE Level with Python Sue Sentance Sue.sentance@anglia.ac.uk
Teaching Computing…
…to GCSE Level with Python
Sue Sentance

2. Course overview Week No Date Computing Theory (5:30 – 6:30)
Programming in Python
(6:30 – 8:00) 1
15/01/2013
Structure of the course
Introduction to Binary
Variables/assignment 2
22/01/2013
More binary logic/hex
Selection 3
29/01/2013
Truth tables/logic diagrams
Iteration 4
05/02/2013
Structure of the processor
Iteration/Lists 5
12/02/2013
(start 6pm)
Algorithms and Dry Runs
More on lists 6
26/02/2013
The internet
Functions 7
05/03/2013
Networking/ HTML and CSS
Files 8
12/03/2013
Database theory
Databases 9
19/03/2013
GCSE Controlled Assessment Tasks 10
26/03/2013
Consolidation

3. 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

4. OCR GCSE Computing
3 units A451 – Theory (Examination) A452 – Practical investigation (Controlled Assessment) A453 – Programming (Controlled Assignment)

5. AQA Computer Science Component 1 – Practical programming
50 hours controlled assessment
Worth 60%
Component 2 – Computing fundamentals
1 ½ hour examination
Worth 40%

6. Today’s session
4:45 – 5:45 Binary & Binary arithmetic/ Hex 6.00 – 7.30 Starting to program in Python

7. From the specification
OCR
(a) define the terms bit, nibble, byte, kilobyte, megabyte, gigabyte, terabyte
(b) understand that data needs to be converted into a binary format to be pro
(c) convert positive denary whole numbers (0-255) into 8-bit binary numbers and vice versa
(d) add two 8-bit binary integers and explain overflow errors which may occur
(e) convert positive denary whole numbers (0-255) into 2-digit hexadecim
AQA
understand that computers use the binary alphabet to represent all data and instructions
understand the terms bit, nibble, byte, kilobyte, megabyte gigabyte and terabyte
understand that a binary code could represent different types of data such as text, image, sound, integer, date, real number
understand how binary can be used to represent positive whole numbers (up to 255)
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

8. Binary numbers

9. Binary numbers 1

10. Learning binary numbers
Converting binary to denary
Converting denary to binary
Binary addition

11. 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

12. What is meant by? 1 byte ? 1 nibble ? 1 kilobyte ? 1 megabyte ?
1 gigabyte ?
1 terabyte ?

13. Storing data
1 byte
1 nibble
1 kilobyte
1 megabyte
1 gigabyte
1 terabyte
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

14. Activity Binary counting exercise

15. How to convert Binary Numbers to denary
Place values 1 2
128 64 32 16 8 4
= 155
in Denary

16. Storing Numbers - Binary
EXAMPLE
Convert the binary number into denary:
Answer
= =183

17. Conversion Exercise Convert the following binary numbers into denary:

18. Teaching binary Holding cards up activity Finger binary
Cisco binary game
CS Unplugged actitivies

19. Converting Denary to Binary
Write down the column headings for the binary number:
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.

20. Convert to Binary

21. Sizes of Binary Numbers
If we have 4 bits available the largest number is (which is 15 in denary)
If we have 5 bits available the largest number is (denary value 31)
If we have 7 bits available the largest number is (denary value 127)
If we have 8 bits available the largest number is (denary value 255)
Can you see a pattern?
animated

22. To calculate the max size
In general if we have n bits available then the largest denary number we can store is
2n - 1
For example, for 3 bits, 1112 = 23 – 1 = 8 – 1 = 7

23. Addition Rules for Binary
0 + 0 = 0
1 + 0 = 1
0 + 1 = 1
1 + 1 = 10 (write down 0 and carry 1)
= 11 (write down 1 and carry 1)

24. check the answer using place values: 8+4+0+1 = 13
Adding Binary Numbers
add 8 and 5 13 1 1 1
check the answer using place values:
= 13

25. check the answer using place values: 8+4+2+0 = 14
Adding Binary Numbers
add 9 and 5 1
carry 14 1 1 1
check the answer using place values:
= 14

26. Exercises – see sheet