These data files usually remain constant throughout a game: it's rather painful to change them in mid-game while avoiding Tim Continuum attacks. Both the host and the players must use exactly the same data set.

Some of these files are some bytes longer than required. These bytes are not used and contain only parts of deleted files on Wisseman's hard disk.

Tim's CONFIG.SYS was exactly 215 bytes large on 9/May/1992 at 9:03 pm.

The ship specification files need to have fixed sizes checked for by PLANETS.EXE:

    BEAMSPEC.DAT        360 bytes
    ENGSPEC.DAT         598 bytes (4 bytes more than required)
    HULLSPEC.DAT        6300 bytes
    TORPSPEC.DAT        470 bytes (90 bytes more than required)
  PLANETS.EXE computes a checksum each time it is started to prevent using
  modified files. The sum of all bytes of these 4 files must be exactly
  338817. Otherwise Planets refuses to run with the message
   "ERROR: Main data files have been tampered with."
  However, the 94 superfluous bytes should be enough to compensate changes.

TRUEHULL.DAT is 940 bytes by default, of which only 440 are needed.