The general types of GUIDs include:
Random: Uses a system to generate a random, 128-bit number
Time-based: Creates a GUID based on the current time
Hardware-based: Makes a GUID with certain portions based on hardware features, such as the MAC address of a network card.
Content-based (MD5 or SHA-1 hash of data): Creates a GUID based on a hash of the file contents. Files with the same contents will be assigned the same GUID.
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