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Teaching Computing…
…to GCSE Level with Python
Sue Sentance
[email protected]
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