THE '.ins' INSTRUCTION FILE - GENERAL ORGANIZATION

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).

There is also a facility (which may not be possible under some operating systems) for reading instructions from (possibly nested) 'include files' by inserting the line '+filename' at the appropriate place in the '.ins' file.

A number of instructions allow atom names to be referenced; use of such instructions without any atom names means 'all non-hydrogen atoms' (in the current residue, if one has been defined). A list of atom names may also be abbreviated to the first atom, the symbol '>' (separated by spaces), and then the last atom; this means 'all atoms between and including the two named atoms but excluding hydrogens'. For further details of the atom list syntax, see RESI as well as the following examples.

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