The Floppy Almanac was the first accurate astronomical ephemeris program for personal computers, and the first computer application produced by the U.S. Naval Observatory for unlimited distribution. The Floppy Almanac was developed in the mid-1980s and was designed to run on the earliest Intel-based PCs: a hard disk was not needed, and the program could execute on a computer with only 256K of memory (some calculations were, however, a bit sluggish!). The executable was self-contained (no external files were required) and the entire product fit on one 360K floppy diskette. Just like its paper counterpart, the Astronomical Almanac, there were separate editions for each calendar year. Distribution of the first two Floppy Almanac editions, for the years 1986 and 1987, started in the fall of 1986. The Floppy Almanac rapidly became popular.
One of the features of the original Floppy Almanac was that the source code was entirely written in ANSI standard Fortran 77 and the user interface was written for a "dumb" terminal. This meant that the Floppy Almanac was easily portable to many kinds of computers, and versions for IBM 370 mainframe systems and DEC MicroVAX systems were made available. By the late 1980s, a friendlier user interface was created, but it was of necessity PC-specific. At the time, portability seemed less important than ease of use for the large number of PC users. A few other new features were also added. A version of the Floppy Almanac that provided data for extended periods of time—the Interactive Computer Ephemeris (ICE)—was also developed.
The Floppy Almanac was superseded in 1993 by Version 1.0 of MICA, the Multiyear Interactive Computer Almanac. This first version of MICA, for both DOS-based PCs and Macintosh systems, had a much more modern user interface than did the Floppy Almanac, provided a wider range of tabulations, and supplied astronomical data for a ten-year span. MICA has been continually upgraded since then.
The Floppy Almanac is no longer being developed or supported by the Naval Observatory.