TOSEC (The Old School Emulation Center) is a project dedicated to create complete databases of software for each computer system. Each database is stored in a .dat file which can then be used by a ROM manager to arrange, sort, rename... etc a users own ROM collection.
TOSEC dat files are great to obtain a near to complete list of all known software for a given platform. This is perfect for collectors as they can run their software collection through a ROM manager to check their files are named correctly, pass crc checks, and to see if they are missing anything in their collection.