Computer Science Paper 1
● Data representation
● Data transmission
● Hardware
● Software
● The internet and its uses
● Automated and Emerging technologies
Data representation
Any information needs to be converted into BINARY
Binary:
- Base 2 number system
- 2 values → 1 (ON) and 0 (OFF)
- Switches
- Logic gates
Denary:
- Base 10 number system
Hexadecimal:
- Base 16 number system
Programmers find hexadecimal more convenient:
❖ 1 hex represents 4 binary digits → more compact
❖ Easier to read, write and copy
❖ Less prone to errors
USES OF HEXADECIMAL (EMIH)
❖ Error codes
❖ MAC address (Media access and control)
❖ IP address (internet protocol)
❖ HTML (hypertext markup language)
,Overflow Error → extra bit → register may have a fixed size → thus extra bit is log
Logical Shift
- Left → x2 1 = x2 2 = x4 3 = x8
- Right → ÷2 1 = ÷2 2 = ÷4 3 = ÷8
- Registers often have a 8 bit limit
- Multiplying can cause bits to be lost
- Losing the most significant bit
Two's Complement
- Used to represent negative numbers
If start digit:
0 = positive
1 = negative
Text
- Every character is represented by binary code
- Character set: collection of characters and symbols that have been defined or recognised by the computer,
each character and symbol has a unique value.
ASCII
UNICODE
ASCII UNICODE
Unique 8 bit binary code Uses 16 to 32 bits
UC, LC, digits and punctuation marks Characters in different languages can be represented
Uses values 0 to 127 Emojis
128 to 256 characters Unicode has 60 thousand to 4 billion characters
1 byte for 1 character 4 bytes for 1 character
Characters used in other language can be represented
Disadvantage for using UNICODE
More bits per character can result in a larger file size and slow processing times when working with text based data
, Sound (is analogue as it varies continuously)
- Analog sound is Captured and recorded using microphone
- The sound wave is sampled at regular time intervals to measure the amplitude
- This gives an approximate representation of sound waves
- Each amplitude has a unique binary value
- The sample rate is set which is the number of samples taken per second
- The sample resolution is set which is the number of bits used for each sample
- Each sample taken is converted to binary
Sampling Resolution (Bit depth)
- Number of bits used to represent sound amplitude in digital sound recording
- Increase sampling resolution
Gives more accurate representation of sound wave
Greater quality
Increase file size
Sample Rate
- The number of sound samples taken per second
1Hz = 1 sample per second
- Increasing sample rate
Gives a more accurate representation
Greater quality
Increase file size
pros and cons of increasing sample rate/resolution
● Data representation
● Data transmission
● Hardware
● Software
● The internet and its uses
● Automated and Emerging technologies
Data representation
Any information needs to be converted into BINARY
Binary:
- Base 2 number system
- 2 values → 1 (ON) and 0 (OFF)
- Switches
- Logic gates
Denary:
- Base 10 number system
Hexadecimal:
- Base 16 number system
Programmers find hexadecimal more convenient:
❖ 1 hex represents 4 binary digits → more compact
❖ Easier to read, write and copy
❖ Less prone to errors
USES OF HEXADECIMAL (EMIH)
❖ Error codes
❖ MAC address (Media access and control)
❖ IP address (internet protocol)
❖ HTML (hypertext markup language)
,Overflow Error → extra bit → register may have a fixed size → thus extra bit is log
Logical Shift
- Left → x2 1 = x2 2 = x4 3 = x8
- Right → ÷2 1 = ÷2 2 = ÷4 3 = ÷8
- Registers often have a 8 bit limit
- Multiplying can cause bits to be lost
- Losing the most significant bit
Two's Complement
- Used to represent negative numbers
If start digit:
0 = positive
1 = negative
Text
- Every character is represented by binary code
- Character set: collection of characters and symbols that have been defined or recognised by the computer,
each character and symbol has a unique value.
ASCII
UNICODE
ASCII UNICODE
Unique 8 bit binary code Uses 16 to 32 bits
UC, LC, digits and punctuation marks Characters in different languages can be represented
Uses values 0 to 127 Emojis
128 to 256 characters Unicode has 60 thousand to 4 billion characters
1 byte for 1 character 4 bytes for 1 character
Characters used in other language can be represented
Disadvantage for using UNICODE
More bits per character can result in a larger file size and slow processing times when working with text based data
, Sound (is analogue as it varies continuously)
- Analog sound is Captured and recorded using microphone
- The sound wave is sampled at regular time intervals to measure the amplitude
- This gives an approximate representation of sound waves
- Each amplitude has a unique binary value
- The sample rate is set which is the number of samples taken per second
- The sample resolution is set which is the number of bits used for each sample
- Each sample taken is converted to binary
Sampling Resolution (Bit depth)
- Number of bits used to represent sound amplitude in digital sound recording
- Increase sampling resolution
Gives more accurate representation of sound wave
Greater quality
Increase file size
Sample Rate
- The number of sound samples taken per second
1Hz = 1 sample per second
- Increasing sample rate
Gives a more accurate representation
Greater quality
Increase file size
pros and cons of increasing sample rate/resolution
