MOJZA
O Levels & IGCSE
COMPUTER
SCIENCE NOTES
Paper 1: Computer Systems
2210 & 0478
BY TEAM MOJZA
, MOJZA`
CONTENTS
Pg 02 Unit 1 Data Representation
Pg 10 Unit 2 Data Transmission
Pg 18 Unit 3 Hardware
Pg 46 Unit 4 Software
Pg 54 Unit 5 Internet and its Uses
Pg 69 Unit 6 Automated Systems
1
, MOJZA`
Unit 1: Data Representation
Uses of Binary System
➔ To process data in logic gates/transistors
➔ To store data in registers
➔ To process data on the computer
Differences between Denary, Binary and Hexadecimal
Denary Binary Hexadecimal
Base 10 system Base 2 system Base 16 system
Used in counting and Used to store data in registers Used in MAC addresses, IP
calculation in daily life and process data in logic gates addresses, HTML colour
and computers codes, error codes, etc.
Uses the digits 0 to 9 Uses 0s and 1s Uses digits 0 to 9 and
alphabets A to F
Has fewer digits for the same Has more digits for the same Has fewer digits for the same
value value value
How and why is hexadecimal used as a beneficial method of data
representation?
➔ Used in colour codes, error codes and IP & MAC addresses
➔ Easily understandable
➔ Easier to debug
➔ Takes less space on the screen
2
, MOJZA`
Data Conversions
- Binary to Denary
➔ Convert 11101110 to denary
128 64 32 16 08 04 02 01
1 1 1 0 1 1 1 0
11101110 = 128 + 64 + 32 + 08 + 04 + 02 = 238
- Denary to Binary
➔ Method #1: Subtracting with the largest possible power of 2.
Convert 142 to Binary
142 - 128 = 14 - 8 = 6 - 4 = 2 - 2 = 0
➔ Method #2: Successive division by 2
DIV MOD
142 0
71 1
35 1
17 1
8 0
4 0
2 0
1 0
0 1
142 = 10001110
3
O Levels & IGCSE
COMPUTER
SCIENCE NOTES
Paper 1: Computer Systems
2210 & 0478
BY TEAM MOJZA
, MOJZA`
CONTENTS
Pg 02 Unit 1 Data Representation
Pg 10 Unit 2 Data Transmission
Pg 18 Unit 3 Hardware
Pg 46 Unit 4 Software
Pg 54 Unit 5 Internet and its Uses
Pg 69 Unit 6 Automated Systems
1
, MOJZA`
Unit 1: Data Representation
Uses of Binary System
➔ To process data in logic gates/transistors
➔ To store data in registers
➔ To process data on the computer
Differences between Denary, Binary and Hexadecimal
Denary Binary Hexadecimal
Base 10 system Base 2 system Base 16 system
Used in counting and Used to store data in registers Used in MAC addresses, IP
calculation in daily life and process data in logic gates addresses, HTML colour
and computers codes, error codes, etc.
Uses the digits 0 to 9 Uses 0s and 1s Uses digits 0 to 9 and
alphabets A to F
Has fewer digits for the same Has more digits for the same Has fewer digits for the same
value value value
How and why is hexadecimal used as a beneficial method of data
representation?
➔ Used in colour codes, error codes and IP & MAC addresses
➔ Easily understandable
➔ Easier to debug
➔ Takes less space on the screen
2
, MOJZA`
Data Conversions
- Binary to Denary
➔ Convert 11101110 to denary
128 64 32 16 08 04 02 01
1 1 1 0 1 1 1 0
11101110 = 128 + 64 + 32 + 08 + 04 + 02 = 238
- Denary to Binary
➔ Method #1: Subtracting with the largest possible power of 2.
Convert 142 to Binary
142 - 128 = 14 - 8 = 6 - 4 = 2 - 2 = 0
➔ Method #2: Successive division by 2
DIV MOD
142 0
71 1
35 1
17 1
8 0
4 0
2 0
1 0
0 1
142 = 10001110
3
