The d*TREK reflnlist format is extensible much like the MTZ format.
There are binary and ASCII versions.  I think that for a start, I'll
describe just the file that is output at the end by our scaling and
averaging program.  This file is the one most users will use for
subsequent steps.

The file is ASCII free-format and consists of the following lines:

Line 1: 3 or 4 integer numbers
        The first 3 numbers represents the number of fields or columns per
        reflection.
        1st number: Number of integer fields: NumInts
        2nd number: Number of float fields:   NumFloats
        3rd number: Number of string fields:  NumStrings
        The fourth number, NumInfoLines, may not be present.  It
        represents the number of lines of additional header text that
        follows the first line.  If absent, this number should be set to 0.

If NumInfoLines is not 0, then NumInfoLines containing d*TREK header
       keyword=value(s); information follows.  If NumInfoLines is 0, then
there are no such lines. Presently, these lines contain information about
the crystal unit cell and spacegroup.  In the future, these lines could
contain an entire standard d*TREK header which could fully describe the
experiments and processing to yield the reflns in the file.

Lines 2+NumInfoLines ....
These contain left-justified the names of the refln fields or columns.
Field names have no white space; one field name per line.  Integer
field names begin with the letter n; float field names with the letter f;
string field names with the letter s.  There will be
NumInts + NumFloats + NumStrings fieldnames.  The first 3 integer
field names MUST be nH, nK, nL.  The first 2 float field names MUST be
fIntensity and fSigmaI.  All integer fields come before any float fields.
All string field follow any float fields.

Lines 2+NumInfoLines + NumInts + NumFloats + NumStrings ...
These are the actual reflns.  Reflns MUST contain h, k, l as integers and
Intensity and SigmaI as floats.  All other fields are optional.  Any
strings cannot have whitespace.  The reflns MUST have a value for
every field.  The values -1.0 and -999.0 are often used as fillers.
All values are in free format and NOT RESTRICTED NOR ALIGNED IN ANY
COLUMNS.

Next is a short example of a reflnlist file produced by dtscaleaverage:

=====this is an example reflnlist file====(do not include this line)===
3 6 0 5
CRYSTAL_DESCRIPTION=unknown;
CRYSTAL_MOSAICITY=0.7807 0.0000 0.0000;
CRYSTAL_ORIENT_ANGLES= 7.3764  -13.6663  -11.2194;
CRYSTAL_SPACEGROUP=89;
CRYSTAL_UNIT_CELL= 78.6619  78.6619  36.9993  90.0000  90.0000  90.0000;
nH
nK
nL
fIntensity
fSigmaI
fIntensity+
fSigmaI+
fIntensity-
fSigmaI-
    0    0    2 14.9526 51.0419 14.9526 51.0419 -1.00000 -1.00000
    0    0    3 112.983 44.0395 99.7694 71.9012 119.599 50.8736
    0    0    4 45164.7 2055.19 45164.7 2055.19 -1.00000 -1.00000
    0    0    5 100.449 52.7485 100.449 52.7485 -1.00000 -1.00000
    0    0    6 45.1334 57.8072 45.1334 57.8072 -1.00000 -1.00000
    0    0    7 104.904 75.1638 104.904 75.1638 -1.00000 -1.00000
    0    0    8 46159.0 1567.61 46159.0 1567.61 -1.00000 -1.00000
    2    1   16 3622.38 130.607 3380.38 172.233 3935.93 196.389
    2    1   17 3799.84 133.226 4082.16 193.255 3543.54 183.439
    2    2    1 39556.5 871.160 40230.6 1249.37 38917.1 1214.40
    2    2    2 43025.1 1156.39 43240.7 2109.55 42863.4 948.015
======================do not include this line either ==============

The fields fIntensity+, fSigmaI+, fIntensity-, fSigmaI- hold values for
the anomalous intensity information.  The values fIntensity and fSigmaI
hold the properly weighted average for Intensity and sigmaIntensity.  The
fields fIntensity+, fSigmaI+, fIntensity-, fSigmaI- MAY NOT ALWAYS BE
PRESENT in the file since this is under user control.  A zero or negative
value for any Sigma means the intensity:sigma pair is not valid and should
be considered absent or rejected.  Negatives values for Intensity are
allowed and valid if the corresponding sigma is positive.  Values of (-1,
-1) for (Intensity, Sigma) mean the measurement is absent.  Centric
reflections will still have I+ and I- measurements even though this should
be equivalent.

Here is another example file:

=====this is an example reflnlist file====(do not include this line)===
3 6 0
nH
nK
nL
fIntensity
fSigmaI
    0    0    2 14.9526 51.0419
    0    0    3 112.983 44.0395
    0    0    4 45164.7 2055.19
======================do not include this line either ==============
