Text, Sound and Images Flashcards
(24 cards)
What is a character set?
A character set is all the characters and symbols that can be represented by a computer system where each character is given a unique binary code.
State two character sets
ASCII and UNICODE
Characteristics of ASCII
7-bits, 128 characters and used to represent characters in only the English language.
Characteristics of UNICODE
16-bits, 65,536 characters and used to represent characters across the world.
Benefit of ASCII
It uses a lot less storage space than UNICODE.
Benefits of UNICODE
It can represent more characters than ASCII.
It can support all common characters across the world.
It can represent special characters such as emoji’s.
Drawbacks of ASCII
It can only represent 128 characters.
It cannot store special characters such as emoji’s.
Drawbacks of UNICODE
It uses a lot more storage space than ASCII.
Define sample rate
Sample rate is the amount of samples taken per second of the analogue wave.
Define sample resolution
Sample resolution is the number of bits stored per sample of sound.
Define Image Resolution
Resolution is the total amount of pixels that make up a bitmap image
The resolution is calculated by multiplying the height and width of the image (in pixels)
Define pixel
A pixel is the smallest component of a bitmap image and is stored as a binary code. It is one circle of colour.
Define Colour Depth
Colour depth is the number of bits stored per pixel in a bitmap image
The colour depth is dependent on the number of colours needed in the image
Image file size calculation
Image height x Image width x colour depth
(Image resolution)
Sound file size calculation
Sample rate (HZ) x Sample resolution (bits) x length of sound sample (s)
*For a stereo file just multiply it by two
Describe packet switching (5)
Data is split and divided into packets
Each packet takes a different route
A router controls the route a packet takes
Selecting the shortest available route
Packets may arrive out of order
Once the last packet has arrived they are reordered
If a packet is missing, it is requested again.
Advantages of packet switching
Interference and corruption are minimal as individual packets can be resent if they are lost or damaged
The whole file doesn’t need to be resent if a corruption occurs, this saves time and internet bandwidth
Packet switching is quicker than sending a large packet as each packet finds the quickest way around the network
It’s harder to hack an individual’s data as each packet contains minimal data, and travels through the network separately
What is data transmission?
Data transmission is the process of transferring data from one device to another using a wired or wireless connection.
Describe serial data transmission
A stream of bits is sent in sequence, one after the other over a single wire/channel.
Describe parallel data transmission
A stream of several bits of data is sent in sequence, one after the other across multiple wires at the same time.
Advantages of serial data transmission
Data wont be skewed
Less chance of interference or errors
Transmission speed is adequate
Disadvantage of serial data transmission
Slow transmission speed
Disadvantages of parallel data transmission.
Parallel is not suitable for long distances
Data could become skewed
Parallel cables aren’t manufactured longer than 5m.
Advantage of parallel data transmission
Very fast transmission speed which is suitable for short distances.
