meant to be visible to the Acorn computer, whether real or emulated, but otherwise their meaning has not been specified. Chunks providing content information include the file origin chunk, which identifies the application that generated the UEF file. Inlay scan chunks, intended as a file preview, hold a raw bitmap of the cover art although anything beyond a thumbnail can take up more data than a typical game. The UEF author can also provide the text of an instruction booklet or a URL for more information, a short title for display, minimum machine specification and keyboard mapping for the enclosed software; and where a game does not use the whole screen, the coordinates of the visible area can be given. A minority of UEF files available online contain anything in this class but an origin chunk. A UEF file can contain multiple classes of data at once, as Harte intended; it is not possible to know which classes it contains without scanning the whole file. In its file selection box ElectrEm displays an icon according to the first data class chunk it finds. Applications MakeUEF MakeUEF is a Windows application written by Thomas Harte and expanded by Fraser Ross to convert audio samples into UEF files. Two grades are offered. An 'amateur' version reads WAV files or a live signal played to the sound card, and transcribes only standard data blocks with accuracy. The 'professional' grade accepts only CSW files, which represent waves preprocessed into rectangular pulse trains, but it encodes all audio information supported by the UEF specification. MakeUEF claims to have been the sole creator of all UEF files available on the Web before November 2004, the month of its version 1.0 release. Although the file format was more capable, supporting "gap lengths" since February 2001 at the latest, only "program data" was retained by MakeUEF prior to version 1.0. From November 2004 the fidelity of MakeUEF improved and the file spec was further refined, and an extension of .hq.uef ("high quality") was adopted to reflect this. The AcornPreservation.org archive only carries the HQ.UEF variety as well as the CSW source files. Its sister site StairwayToHell.com accepts 'amateur' UEF translations and files produced by pre-1.0 MakeUEF. the latter site hosts 1,494 transcriptions of BBC Micro cassette titles and at least 800 of Electron titles. Others Several emulators of Acorn machines support UEF natively, to read and write tape