Unified Emulator Format (UEF) is a container format for the compressed storage of audio tapes, ROMs, floppy discs and machine state snapshots for the 8-bit range of computers manufactured by Acorn Computers. First implemented by Thomas Harte's ElectrEm emulator and related tools, it is now supported by major emulators of Acorn machines and carried by two online archives of Acorn software numbering thousands of titles. UEF attempts to concisely reproduce media borne signals rather than simply the data represented by them, the intention being an accurate archive of original media rather than merely a capability to reproduce files stored on them. A selection of metadata can be included, such as compatibility ratings, position markers, images of packaging and the text of instruction manuals. The Acorn machines implement the Kansas City standard (KCS) for tape data encoding and as a result the file format is suitable for creating backups of original media for several non-Acorn machines. As of version 0.10 the file format carries BASICODE signals as well. TZX is a chunked format with similar scope for the ZX Spectrum series. History Before the development of the UEF, archives of Acorn computer software on the World Wide Web had adopted a convention of hosting ZIP archives of the raw files on a tape, each raw file accompanied by a sidecar file, with extension .inf, carrying the load and execution addresses from the file header. The INF convention, described and implemented by Wouter Scholten in bbcim (1995), extends the output format of the *INFO command (built into Acorn DFS and ADFS, which lists file lengths and other metadata attached to files on disc) to cover CRCs and the order of files on tape. While it works adequately for storing user files, it does not preserve the baud rate of the recording, precise timing information or the non-standard data streams used in copy protected titles. In the case of disc-based software, it became increasingly convenient to send a sector dump of the disc instead, and by the time of the UEF's introduction the file extensions .ssd and .dsd were already established for single-sided and double-sided raw images of DFS discs, respectively. Distributed bare or in a ZIP archive, they remain popular on archive sites. Aims In a 2010 post to the Stardot forum, Harte explained at length his reasons for creating the format: being the first to address emulation of the Acorn Electron