INS MODEL FILE
The .INS instruction file - general organisation.
All instructions commence with a four (or fewer) character word (which may be
an atom name); numbers and other information follow in free format, separated
by one or more spaces. Upper and lower case input may be freely mixed; with
the exception of the text string input using TITL, the input is converted to
upper case for internal use in SHELXL_93. The TITL, CELL, ZERR, LATT (if
required), SYMM (if required), SFAC, DISP (if required) and UNIT instructions
must be given in that order; all remaining instructions, atoms, etc. should
come between UNIT and the last instruction, which is always HKLF (to read in
reflection data).