Int 2 Computing
Mr Arthur
Course Outline
3 Main Units Computer Systems = 40 hours Software Development = 40 hours Artificial Intelligence = 40 hours
Assessment 3 End of Unit Assessments (NABS /20) 2 Practical Coursework Tasks (/15 - 30%) Written Exam (/70 or 70%)
Computer Systems
5 units in the Computer Systems Section1. Data Representation = 6 hours
2. Computer Structure = 7 hours
3. Peripherals = 5 hours
4. Networking = 9 hours
5. Computer Software = 9 hours
Aims of Lesson 1
1. How are numbers, text and images represented inside the computer system?
2. Discussing the 2 state computer system
3. Converting positive whole numbers to binary and vice versa
4. Playing Binary Bingo
Data Representation
100 billion switches per sq. cm
Data Storage
Numbers, Text, and Images are all stored as a series of 1s and 0s inside the computer system.
These series of 1s and 0s are made up of pulses of electricity from 1 volt to 5 volts
Decimal Counting System
When we represent numbers we use the decimal counting system, for example
123,000
100,000 10,000 1,000 100 10 1
1 2 3 0 0 0 Since the computer is 2 state, the binary counting
system goes up by the power 2, rather than 10 i.e
256 128 64 32 16 8 4 2 1
How Positive Whole Numbers are Stored
34
128 64 32 16 8 4 2 1
0 0 1 0 0 0 1 0
= 32 + 2 134
128 64 32 16 8 4 2 1
1 0 0 0 0 1 1 0
= 128 + 4 + 2
Binary back to Decimal
1011 0011
128 64 32 16 8 4 2 1
1 0 1 1 0 0 1 1
= 128 + 32 + 16 + 2 + 1
=179
Binary Bingo 42 81 21 16 121 73 101 75 127 128
13 209 32 56 175 192 186 176 121 250 34
Aims of Lesson 2
1. Data Units1. Bits/Bytes etc
2. Floating Point Representation
Storage Capacities
0 or 1 = 1 bit
8 bits = 1 byte
1024 bytes = 1 Kilobyte
1024 Kilobytes = 1 Megabyte
1024 Megabytes = 1 Gigabyte
1024 Gigabytes = 1 Terabyte
Representing Non Whole Numbers
How do we represent the number 128.75 in binary?
128 + 0.5 + 0.25 = 128.75
128 64 32 16 8 4 2 1 0.5 0.25 0.125 0.0625
1 0 0 0 0 0 0 0 1 1 0 0
Mantissa and Exponent
Mantissa
Exponent
8
8 4 2 1
1 0 0 0
128 64 32 16 8 4 2 1 0.5 0.25 0.125 0.0625
1 0 0 0 0 0 0 0 1 1 0 0
1 0 0 0 0 0 0 0 1 1 0 0
Mantissa
Exponent
6
8 4 2 1
0 1 1 0
1 0 0 1 1 0 0 0 1 0
1 0 0 1 1 0 0 0 1 0
How do we represent the number 38.125 using floating point
32 16 8 4 2 1 0.5 0.25 0.125 0.0625
Representing Non Whole Numbers
Mantissa relates to the precision of the number you can represent i.e 34.44454321
Exponent relates to the position of the decimal point
8 4 2 1 0.5 0.25 0.125 0.075 0.0375 0.01875 0.009375
Aims of Lesson 3
1. Representing Graphics1. Pixels
2. Resolution
2. Graphics Calculations
Pixels/Resolution
Pixel Stands for Picture Element A pixel is a dot on the screen. It is a graphic
segmented up into its simplest form Resolution
This is the numbers of pixels there are per inch (dpi)
The higher the resolution the higher the quality of the image
BIT Map GraphicsSCREEN MEMORY
PIXEL
MEMORY REQUIRED
8 BITS X 8 BITS = 64 BITS
= 8 BYTES
Bit Map = the graphic is made up from a series of pixels
Graphics Resolution
The smaller the size of the pixels, the finer the detail of the image
800 x 600 pixels lower quality than 1024 x 768
As the number of pixels increases so does the storage space required
Pixel Pattern using 8x8 grid
Pixel Pattern using 16x16 grid
Calculating Storage Capacities of Bit Mapped Images
Storage Requirements = total number of pixels * number of bits used for each pixel
This picture of Mr Haggarty has a resolution of 300dpi. The image is 2 inches by 4 inches in 128 colours
300 X 2 = width 600 pixels
300 X 4 = height 1200 pixels
Total pixels = 600 X 1200 = 720,000 pixels
Each pixel = 7 bits i.e. 2 = 128 colours
720,000 X 7 = 5,040,000 bits / 8 = 630,000 bytes
630,000 / 1024 = 615Kb
7
Aims of Lesson 4
Last Lessons
1. Representing whole numbers
Decimal to Binary Binary to Decimal
2. Non-whole numbers Floating Point
3. Data Units
4. Representing Graphics1. Pixels
2. Resolution
5. Graphics Calculations
Today’s Lesson 1. Representing Text2. Advantages of using binary
How is Text Represented ASCII
Each key on the keyboard is converted into a binary code using 7 bits
Using 7 bits i.e 2 = 128 characters can be represented
Character Set A list of all the characters
which the computer can process
Control Characters Codes 0 to 31 are non
printable characters, for example tab, return, alt
7
Character Binary Decimal
tab 000 1001 9
return 000 1101 13
space 010 0000 32
! 010 0001 33
‘ 010 0010 34
1 011 0001 49
A 100 0001 65
a 110 0001 97
Binary Message
1010100 1001000 1001001 1010011
0100000 1010111 1000101 1000001
1010100 1001000 1000101 1010010
0100000 1001001 1010011 0100000
1001000 1001111 1010010 1010010
1001001 1000010 1001100 1000101
Advantages of Using Binary
Computers are 2 state e.g. on and off and Binary is a 2 state counting system e.g. 1010
If there is any drop in voltage (degradation) the pixel etc is still represented as a 1 (black)