This functionality soon appeared in commercial products, such as Pronto-DOS, Diversi-DOS, Hyper-DOS, and David-DOS, along with additional features, but it was never used in an official Apple DOS release. Similar functionality was, however, employed by Apple's successor operating system, ProDOS. The Apple IIGS-specific operating system, GS/OS, would eventually employ an even more efficient "scatter read" technique that would read any sector that happened to be passing under the read head if it was needed for the file being read.