1: Information Representation
Kibi is binary prefix and kilo is denary prefix
BCD is used to represent values in a clock or calculator
- Straightforward to convert BCD to Denary vice versa
- So less complex to encode and decode for programmers
- Easier for digital equipment use BCD to display output information
- Can represent monetary values exactly
Character set:
- All of the characters that computer can use
- Each character has a unique number
ASCII – 128/ 27
Extended ASCII – 256/ 28
- Each character has its own unique code
- Each character in the word is replaced by its code
- The codes are stored in the order in the word
Unicode:
Has characters from other languages
16 or 32 bits
Pixel:
- Single square of colour
- Smallest addressable element in an image
File Header:
- Colour depth
- Image resolution
- File type – bitmap or vector
- Compression type
- Location/ offset within data
- dimensions
Bitmap:
- Made of pixels
- Large files
- Pixelated when enlarged
- Can be compressed
- Suitable for photos
- Use little processing power
- Individual elements cannot be grouped
Vector Graphic:
- Set of instructions on how to draw shape
- Small files
- Can enlarge without pixelation
- Cannot compress
- More suitable for geometric shapes
, - Use more processing power
- Individual elements can be grouped
- Need to be rasterised to display or print
Property: data about shapes
Drawing list: the list of shapes involved in an image
Sampling:
• Amplitude of wave is determined
• At set time intervals
• To get approximation of sound wave
• And encoded as a sequence of binary number
+ Increasing sampling rate will improve accuracy of recording
+ Allow for larger dynamic range
+ Less sound distortion
+ Sounds closer to OG
o Smaller time gaps between samples
o Makes digital sound wave more accurate
o Smaller quantisation errors
- Produces larger file size
- Longer to transmit/download sound files
- Greater processing power
Important to estimate file size of image so its possible to estimate how many images can be stored and to decide if it
can be sent as an email attachment.
Image Resolution:
the number of pixels in the bitmap file defined as the product of the width and the height values
Lossy Compression:
Reduce bit depth: reduces number of bits per colour
Reduce colour palette: fewer colours mean fewer bits needed to store each colour
Reduce image resolution: fewer pixels per unit means less binary to store
- human ear will notice decompressed stream will not be identical to original file
- Reduces file size more than lossless
o smaller files takes less time to transit
- Flac (free lossless audio codec)
Cannot Lossy compression on text as:
- No og data can be lost
- Text file would be corrupted
Perceptual music shaping:
method where sounds outside the normal range of hearing of humans, for example, are eliminated from the music
file during compression.
Analogue data = data values that are continuously changing
Lossless Compression:
- File needs to be high precision/accuracy
- None of the original data is lost
,RLE (images) – replace sequences of the same colour pixel with colour code and number of identical pixels
- Lossless
- Reduces string of adjacent identical chars/pixels/bytes
- Encoded into 2 values
- 1st is no. of chars
- 2nd is code of it (e.g. colour)
General compression:
Movie files:
- Reduce sampling rate used
- Reduce sampling resolution
- Reduce frame rate
Image files:
- Crop image
- Decrease bit depth
- Reduce image resolution
2: Communication
LAN: Local area network
- Small geographical area
- No leasing external infrastructure/ does not use internet to transmit within the building.
- Hubs or switches connected to router/modem to allow LAN to join WAN
- Higher data transfer rate
WLAN: (Wireless LAN) LAN without wires or cables
WAPs: (Wireless Access Point) connected into wired network at fixed points. Range from 1 to 100 metres –
receives theough radio signals
WAN: Wide area network
- Cover much larger geographical area, multinational company can connect a number of smaller networks
together to form a world wide WAN
- E.g. ATM (automated teller machine) network – for banks
MAN: Metropolitan area network
having a network:
, + Devices such as printers can be shared
+ Licenses to run software on networks are often far cheaper than individuals
+ Users can share files and data
+ Access to reliable data that comes from a central source – file server
+ Data and files can be backed up centrally
+ Users can communicate using email and instant messaging
+ Network manager can oversee the network and apply access rights
- Cabling and servers can be expensive initially
- Managing a large network is complex and difficult
- Breakdown of servers can affect whole network
- Malware and hacking affect whole network
Network infrastructure:
Hardware:
- LAN cards
- Hubs
o can only broadcast to all connected.
o Directionless transmission.
o All drop packet except one intended to receive.
o Waste of bandwidth
- Switches
o essentially an intelligent hub.
o Sends only to intended recipient.
- Repeater
o Used to boost signals in the wifi zone.
o Sometimes hubs contain repeaters – repeating hubs
One collision domain – ignore this
Referred to as unmanaged since they are unable to manage delivery paths and security
- Routers
same as hub and switch but also has a modem so can connect to outside of network as well.
• In built firewall
o receive packets
o forward packets to destination
o find destination
o allocate private IP address
o routing table
o find most efficient path to destination
o maintain table of IP addresses
- Bridge
o Connects two similar networks
o Occurs at link layer in TCP/IP
o Main function of bridge is to keep the traffic separated on both sides of the bridge
o Format of packet is not changed
- Gateway
o Connects two dissimilar networks
o Packet switches that operate at multiple layers of the OS model
o Translate the protocols so that PCs on the two networks can communicate
o Format of packet is changed
o Do not support dynamic routing
- Modem (modulator demodulator)
o Converts digital to analogue and vice versa
Kibi is binary prefix and kilo is denary prefix
BCD is used to represent values in a clock or calculator
- Straightforward to convert BCD to Denary vice versa
- So less complex to encode and decode for programmers
- Easier for digital equipment use BCD to display output information
- Can represent monetary values exactly
Character set:
- All of the characters that computer can use
- Each character has a unique number
ASCII – 128/ 27
Extended ASCII – 256/ 28
- Each character has its own unique code
- Each character in the word is replaced by its code
- The codes are stored in the order in the word
Unicode:
Has characters from other languages
16 or 32 bits
Pixel:
- Single square of colour
- Smallest addressable element in an image
File Header:
- Colour depth
- Image resolution
- File type – bitmap or vector
- Compression type
- Location/ offset within data
- dimensions
Bitmap:
- Made of pixels
- Large files
- Pixelated when enlarged
- Can be compressed
- Suitable for photos
- Use little processing power
- Individual elements cannot be grouped
Vector Graphic:
- Set of instructions on how to draw shape
- Small files
- Can enlarge without pixelation
- Cannot compress
- More suitable for geometric shapes
, - Use more processing power
- Individual elements can be grouped
- Need to be rasterised to display or print
Property: data about shapes
Drawing list: the list of shapes involved in an image
Sampling:
• Amplitude of wave is determined
• At set time intervals
• To get approximation of sound wave
• And encoded as a sequence of binary number
+ Increasing sampling rate will improve accuracy of recording
+ Allow for larger dynamic range
+ Less sound distortion
+ Sounds closer to OG
o Smaller time gaps between samples
o Makes digital sound wave more accurate
o Smaller quantisation errors
- Produces larger file size
- Longer to transmit/download sound files
- Greater processing power
Important to estimate file size of image so its possible to estimate how many images can be stored and to decide if it
can be sent as an email attachment.
Image Resolution:
the number of pixels in the bitmap file defined as the product of the width and the height values
Lossy Compression:
Reduce bit depth: reduces number of bits per colour
Reduce colour palette: fewer colours mean fewer bits needed to store each colour
Reduce image resolution: fewer pixels per unit means less binary to store
- human ear will notice decompressed stream will not be identical to original file
- Reduces file size more than lossless
o smaller files takes less time to transit
- Flac (free lossless audio codec)
Cannot Lossy compression on text as:
- No og data can be lost
- Text file would be corrupted
Perceptual music shaping:
method where sounds outside the normal range of hearing of humans, for example, are eliminated from the music
file during compression.
Analogue data = data values that are continuously changing
Lossless Compression:
- File needs to be high precision/accuracy
- None of the original data is lost
,RLE (images) – replace sequences of the same colour pixel with colour code and number of identical pixels
- Lossless
- Reduces string of adjacent identical chars/pixels/bytes
- Encoded into 2 values
- 1st is no. of chars
- 2nd is code of it (e.g. colour)
General compression:
Movie files:
- Reduce sampling rate used
- Reduce sampling resolution
- Reduce frame rate
Image files:
- Crop image
- Decrease bit depth
- Reduce image resolution
2: Communication
LAN: Local area network
- Small geographical area
- No leasing external infrastructure/ does not use internet to transmit within the building.
- Hubs or switches connected to router/modem to allow LAN to join WAN
- Higher data transfer rate
WLAN: (Wireless LAN) LAN without wires or cables
WAPs: (Wireless Access Point) connected into wired network at fixed points. Range from 1 to 100 metres –
receives theough radio signals
WAN: Wide area network
- Cover much larger geographical area, multinational company can connect a number of smaller networks
together to form a world wide WAN
- E.g. ATM (automated teller machine) network – for banks
MAN: Metropolitan area network
having a network:
, + Devices such as printers can be shared
+ Licenses to run software on networks are often far cheaper than individuals
+ Users can share files and data
+ Access to reliable data that comes from a central source – file server
+ Data and files can be backed up centrally
+ Users can communicate using email and instant messaging
+ Network manager can oversee the network and apply access rights
- Cabling and servers can be expensive initially
- Managing a large network is complex and difficult
- Breakdown of servers can affect whole network
- Malware and hacking affect whole network
Network infrastructure:
Hardware:
- LAN cards
- Hubs
o can only broadcast to all connected.
o Directionless transmission.
o All drop packet except one intended to receive.
o Waste of bandwidth
- Switches
o essentially an intelligent hub.
o Sends only to intended recipient.
- Repeater
o Used to boost signals in the wifi zone.
o Sometimes hubs contain repeaters – repeating hubs
One collision domain – ignore this
Referred to as unmanaged since they are unable to manage delivery paths and security
- Routers
same as hub and switch but also has a modem so can connect to outside of network as well.
• In built firewall
o receive packets
o forward packets to destination
o find destination
o allocate private IP address
o routing table
o find most efficient path to destination
o maintain table of IP addresses
- Bridge
o Connects two similar networks
o Occurs at link layer in TCP/IP
o Main function of bridge is to keep the traffic separated on both sides of the bridge
o Format of packet is not changed
- Gateway
o Connects two dissimilar networks
o Packet switches that operate at multiple layers of the OS model
o Translate the protocols so that PCs on the two networks can communicate
o Format of packet is changed
o Do not support dynamic routing
- Modem (modulator demodulator)
o Converts digital to analogue and vice versa
