index > 2.1.6 Computer communications and networking
Domain Name Systems
DNS (Domain Name System) are system servers owned by large corporations that contain the IP addresses of millions of websites. They operate within a client to server network in this way:
DNS servers have a database of IP addresses which are constantly updated by other DNS servers. When you request an address (URL like https://www.google.com), the DNS server looks up the URL and returns the IP address (like 74.125.206.147), or searches for the address from other DNS servers. Your browser can then load that web page for you to view.
Advantages
People do not need to remember IP addresses
Easily upgradable (eg IPv4 to IPv6) without all web addresses needing to be the same
As long as you are connected to a DNS server you can have access to all the addresses
There are 2 main types of compression:
Lossy compression: Reduces file size and quality by removing data that won’t be noticed. For example, in images unnoticed colours and details are removed. In music, unnoticed sounds are removed. This reduces the quality. When the data is uncompressed it is not exactly the same as the original but the difference is so small that it cannot normally be noticed.
Lossless compression: Original file keeps the same quality but the size is reduced by noticing patterns and compressing them. E.g. include compressed text files.
