The most common is probably EXE which is for executable files. The oldest would be split between BIN (binary) and TXT (text) files. In music one of the oldest in MIDI which is now mostly used in electric pianos but not commonly used for computers. WMA is one of the original music formats that came out, but it was owned by Microsoft. MP3 is a newer standard and more popular. In video VID was a popular format with the advent of the video disk. But once MPEG-4 came out in conjunction with DVD's, people abandoned the VID format.