Data Representation Flashcards
What is meant by a charecter set?
A group of charecters which can be represented or coded
How many charecters can be represented with the 7-bit ASCII
128 charecters.
What is meant by a bit?
The smallest unit of data a computer can use.
What is the highest value that can be represented by a nibble?
1111
How many bits are there in a byte?
8 bits
How many bytes does 12 bits make?
1.5 bytes
How many megabytes are there in 3 gigabytes?
3000
An overflow error can occur when adding two 8-bit binary values. What is meant by an overflow error?
When the total from adding numbers cannot be stored into the CPU.
Why do people use hexadecimal values to represent numbers stored in computers?
Hexadecimal numbers use less memory so more can be stored.
Why is a check digit used?
To check for errors.
What does ASCII stand for?
American Standard Code for Information Interchange.
Why would Extended ASCII be used?
Extended ASCII would be used for special charecters and has more charecters than ASCII.
What is meant by Unicode?
Unicode is large set of charecters which is used widely because it supports different languages.
What is meant by a Pixel?
The smallest identifiable area of an image.
How many colours can be represented in an image with 8 bits?
256 colours.
Why is metadata included in a file?
The reason why metadata is included in a file is to show information about a picture.
How does the resolution of an image affect the size of the file?
The higher the resolution, the larger the file size will be.
Sampling intervals and other factors affect the size of a sound file and the quality of its playback. What is meant by a bit rate?
The number of bits which determines the range of colours.
How can sound be sampled and stored in digital form?
An analogue converter will capture a sound wave at regular time intervals.
Compression is often used to reduce the size of files before sending them electronically. What is one advantage for compressing files in this way?
To save storage space on media.
What is meant by lossy compression?
Lossy compressions permanently removes some data or uncompressed data is not the same as the original.
What is meant by loseless compression?
Lossless compression does not store repeated data and removes it, allows the original file to be reconstructed the same and has a larger file than lossy compression.
What’s one file standard?
PDF, JPG, GIF, PNG, MP3
How to calculate a file size of a text file
Bits per character X number of characters
How to calculate the file size of a sound file
Sample rate x Duration (s) x bit depth
What is meant by the resolution of an image?
Resolution is the concentration of pixels within a specific area.
Describe what’s meant by colour depth
It determines how many colours can represented in an image.
Give two examples of metadata
Date and time (location can be allowed)
State 2 factors that can affect the file size of a bitmap image
The amount of pixels and colour depth.
Explain the relationship between the image quality and file size.
The higher the image quality, the bigger the file size because better quality , resolution and colour depth increase the size
Describe what’s meant by sound sampling
Taking measurements of amplitude of the wave at regular intervals. These are stored in binary.
The length of a recording will heavily influenxe the size if the sound file. State two factors other than recording length that determine the file seize of a recording
The frequency per second affects the level of detail in digital representation. The greater the frequency, the greater accuracy.
The sampling frequency is the frequency with which measurements are taken more often within the same period of time. How would this affect the quality of the recording?
The more frequently we sample the sound and the more accurately we record the sound wave.
Explain the relationship between the quality of the playback and the file size
As the quality increases, owing to a greater number of samples or a greater sampling accuracy, the more data generated, an therefore the larger the file size
Give two reasons why you might compress photographs files before emailing them to a friend.
To save storage space and to reduce transmission times when sending on a network such as the internet.
Describe 2 benefits of lossy and lossless compression.
Lossy - Allows data to be transmitted faster over a network and suitable for images/video/sound.
Lossless - Removes repeated data and suitable for text/ code files.
