Topic 1-Digital Data Flashcards
Difference between information and data
- An information system processes data and produces information
- Data consists of raw facts and figures with no meaning attached.When data is processed (or given meaning) it produces information
- Therefore data is information
Storing data
- Computers store data in a binary digit form
- A Binary digit (known as a bit) has a value of 1 or 0
- A nibble is represented as 8 bits
- A character (such as a letter or digit) is represented by 1 byte or (8 bits)
- Multiples of bytes are referred to as
- 1 kilobyte(Kb)=1024 bytes
- 1 megabyte(Mb)=1024 kilobytes
- 1 gigabyte (Gb)=1024 megabytes
- 1 terabyte (Tb)=1024 gigabytes
- These terms are used to describe computer memory capacity and the capacity of external storage devices
Data types
Numeric:
- An integer number:
- can be a positive or negative whole number
- has no decimal or fractional parts
- Real numbers:
- include whole numbers (integers) and numbers with decimal/fractional parts
Date/Time:
- Long date is displayed as; Sunday,April 1,2018
- Medium date is displayed as 1-Apr-2018
- Short date is displayed as 01/04/18
- Long time is displayed as 13:26:34
- Medium time is displayed as 01:26PM
- Short time is displayed as 13:26
Character/String
- A character is a single letter or digit represented by the codes from the character set
- ASCII is a character set based on each character being represented uniquely by a single byte
- A string is textual data in the form of a sequence of characters
Representing images
- A pixel is the smallest unit of a digital image that can be displayed and edited
- Each pixel can have its own individual colour and is stored as a series of binary digits
- Combing pixels together will produce a complete image
- The quality of an image is referred to as ‘image resolution’
- The greater the resolution,the greater the file size
- A typical JPEG image uses 24 bits to store a pixel
Bitmap and vector images
- Bitmap graphics store details about every individual element (pixel) of the image
- Storing every pixel means the file size of a bitmap image can be very large
- A bitmap image can also be compressed,which reduces the file size
- Vector-based graphics store information about the components that make up an image
- Components are based on mathematical objects such as lines,curves and shapes
Buffering and streaming a video
- Streaming allows a video to be viewed on a website without a time delay
- Using streaming means the user can start watching the video as it downloads in ‘real time’
- A buffer is part of the memory used to store a downloaded part of the video before watching it
- When the user is watching part of the video a buffer is used to download the next part of the video
- Buffering helps prevent possible disruptions if there are time delays in streaming while the video is playing
Representing sound
Factors that affects sound quality:
-Sample rate-Number of audio sound samples captured per second to represent the sounds digitally
- Bit depth-The number of bits used for each sound sample
- The quantity of data measured in bits that is processed in a given amount of time
Analogue to digital conversion
- An analogue signal is a continuous varying signal that represents a physical quantity
- Examples of analogue signals include sound waves and temperature
- An analogue to digital converter (ADC) will sample a signal at regular time intervals
- Samples are then converted to digital format
- The frequency at which samples are taken is known as the sample rate,measured in Hertz (Hz)
Data portability
- Data portability is the ability to transfer data from one computer to another or form one software application to another without having to re-enter the data.
- This is made possible by using a range of file formats
JPEG
Joint Photographic Expert Group files support the compression of images
TIFF
Tagged Image File Formats store bitmapped images
PNG
Portable Network Graphics allow data compression of bitmapped graphics
PICT
The standard file format for apple graphics
GIF
Graphics Interchange Format supports bitmapped image file format.Animated GIFs combine a series of GIF images and display them one after the other
TXT
A plain text document that contains no text formatting
CSV
A comma-separated value file is a text-format file used by database and spreadsheet applications
RTF
Rich Text Format is used for text-based documents such as word processing
MP3
A file format for compressing sound
MP4
Similar to MP3 but a file format that compresses both sound and video
MIDI
Musical Instrument Digital Interface allows sound samples to be interchanged between different digital musical instruments
MPEG
Moving/Motion Picture Experts Group is a set of standards for compressing digital video
AVI
Audio Video Interleaved is a multimedia file format
Portable Document File is a file format that is read only.The PDF file generated is usually smaller in file size than the original file
WAV
Windows Audio Waveform is a file format standard for storing an audio bit stream on PC’s
WMA
Windows Media Audio is an audio data compression file format
Data compression
- Websites require fast image and audio download speeds
- Reducing the storage requirements of image files and audio files means faster upload and download speeds to and from the internet
- Data compression is used to to reduce file size and at the same time maintain the quality of the data contained in the file
- There are 2 main types of data compression:lossy and lossless
Lossy compression
Lossy compression reduces the file size by removing some data,such as reducing the number of colours used in a small reduction in the quality of an image.JPEG is an example of a lossy compression method
Lossless compression
Lossless compression maintains the quality of the file,therefore no data is lost.An example is WinZip,which reduces the file size for sending data over the internet an it can be recreated (unzipped) exactly as the file was before it was compressed
Pixel
The smallest unit of a digital image that can be displayed and edited on a computer screen
Bitmap graphics
Store details about every individual element (or pixel) that makes up an image
Vector-Based graphics
Store information about the components that make up an image;these components are based on mathematical a objects such as lines,curves and shapes
Streaming
Process that allows video to be viewed on a website straight away without having to wait for the full video to be downloaded
Buffer
Computer memory used to store a part of the video downloaded before it is watched
Data portability
Transferring data from one computer to another or from one software application to another without having to re-enter the data
Define Data compression
Used to convert digital data to convert digital data to as small a size as possible while still maintaining the quality of the data combined in the file;allows data to be sent over the internet with acceptable transmission
