Input of the Crystal Data File

The file holding the Crystal Data contains a sequence of records, each of which will initially be read in the FORMAT (A80), and which, for historical reasons, are referred to as cards . They should be held in a named file; PREFIN, the routine which reads them into the system, will ask for this name.

The first character of every card must be a letter; PREFIN will stop when it encounters a card not starting with a letter (or when it attempts to read beyond the last card in the file). It copies the Crystal Data to an internal unit, from which cards may be read repeatedly as necessary. Empty lines are ignored everywhere in the Crystal Data.

For the first letter on a card, upper and lower case letters are treated alike. In general, though, they are distinct. The character in position 2 on the card, immediately following the letter, is at present ignored, but it should be typed as a space.

The remaining 78 character positions depend on the initial letter. As far as possible the initial letters are mnemonic, like C for cell parameters, A for an atomic position, etc.