File-extensions are created for each new technology and software innovation, but they also need to maintain continuity with previous platforms. This means that, through the intertwining of these platforms and technologies, file-extensions have become a sort of short-hand for the modern history of software development.
As an example we can start with the generic .DAT file extension used, as the name might suggest, for storing data. It’s hard to put a date on which application was the first to create .DAT files, but it’s a pretty reasonable guess to say that it probably goes all the way back to the earliest days of modern PCs as we understand them now, so probably some time in the 70s or 80s.
The .DAT file format is one of the most popular found in computing and a .DAT file could have been created by just about any software available. Applications will create these files simply to store data for their own consumption, although they are commonly used by computer games. Although any text editor will probably be able to open a .DAT file, the precise format of the .DAT file will depend on the program that created it.
Creating and storing raw data output on one computer is simple enough. However when files started to get larger, and needed to be transmitted over networks, you then need to start worrying about the size and integrity of the file (whether errors had been introduced for example). Although file compression has been around at least since IBM’s SQUOZE program in the 1960s, the first popular and widely used compression tool of the PC era was PKZIP.
Developed by the late Phillip Katz, PKZIP was important in making the Internet effective, back in the days when Internet access meant squeezing your content in through a 56K modem. A more recent alternative, developed by Eugene Roshal is the patented .RAR format which, although slower, delivers higher levels of compression than most alternatives. More modern data archiving formats will also offer error recovery and be able to split (and later recombine) larger files into smaller sub-files, for transmission over a network.
So if we have moved from the days of raw data files, on stand alone PCs, through to the advent of large scale networked computing and the related arrival of data compression technologies, we now enter the next stage in data storage and transmission where users are looking to store, and transmit, a richer range of content including music and video, to and from, a broader range of devices that no longer include just PCs, but PDAs and even mobile phones. A popular example of one of the new generation of modern container file formats, popular with mobile phones, is the .3GP data format (and the closely related .3G2).
Defined for use on 3G mobile phones by the Third Generation Partnership Project 3GP files are a multimedia files that, in turn, contain various types of compressed data. Since its launch in 1998 3GP has become the standard format for transferring audio and video files between 3G enabled phones and the Internet. So we can see that the development and evolution of different file types, with their related file extensions, over time, offers a fascinating insight into the evolution of the underlying technology.