Data Compression Flashcards
Describe how a touch screen can be used to input text
A capacitive touch screen is used which consists of a grid of transparent electrodes, the touch screen displays a keyboard, when the screen is touched there is a change in the electrostatic properties at that point which is detected.
Why is compression needed when sending files over the internet
Band width is limited, reducing file sizes on bandwidth, reduces cost of hardware
State the effects compression has on a file
It makes the file smaller
State two advantages for social media on using compressed file formats
Saves space on their servers, quicker to upload to server, web site will load quicker
Explain lossy data compression
Compressed files can never be exactly recovered to what they were before, data is lost, not suitable for textual data because data is lost, it is useful for digitally sampled analogue data, eg. sound video, images. Examples of lossy formats are MPEG, JPEG, MP3
Explain lossless data compression
Original message can be decompressed back to its original form, it works by finding repeating patterns in data and compresses these patters, it does not work well on random messages. Is ideal for text.
Explain why JPEG would be suitable for storing images on a website
Is a standard format, reduces file size by using compression which reduces load time.
Describe the main features of JPEG
Uses image compression reduce file size at the expense of image quality. The degree of looseness can vary to balance file size against quality of image
Describe the main features of bitmap
Each pixel in image is represented using 8/16/24/32 bits. All data is stored and there is no compression meaning file size is large
Describe two advantages of file compression
It reduces the size of a file, decreasing its storage requirements. It reduces the size of file which decreases its send and download times
