127 is a typical roll film. Frame number markings for the 4x4 and 4x6 image formats are printed on the backing paper, while 4x3 camera's typically have two frame counter windows, exposing the left and right half's of the 4x6 frame.
Using the square format, there are 12 exposures, the rectangulars give 16 and 8, respectively.
The format was introduced by Kodak in 1912, along with the Vest Pocket Kodak folding camera, as a compact alternative to the 120. The folding 127s were in fact smaller than most 135 cameras today.
The format was mainly used for amateur cameras, with the Exakta SLR and the Baby Rolleiflex as possible exceptions.
Kodak stopped producing 127 film in 1995. Fotokemika dd of Croatia is one of only two remaining manufacturers of 127 film, which it sells under its own "Efke" brand as well as custom-packaging for other sellers like Maco and Jessops. In addtion to Efke black and white print film, Maco also produce a colour (E6) slide film.