would be longer than 60 characters; otherwise it is padded on the right
with spaces.
+The product name field allow readers to behave differently based on
+quirks in the way that particular software writes system files.
+@xref{Value Labels Records}, for the detail of the quirk that the PSPP
+system file reader tolerates in files written by ReadStat, which has
+@code{https://github.com/WizardMac/ReadStat} in @code{prod_name}.
+
@anchor{layout_code}
@item int32 layout_code;
Normally set to 2, although a few system files have been spotted in
Number of data elements per case. This is the number of variables,
except that long string variables add extra data elements (one for every
8 characters after the first 8). However, string variables do not
-contribute to this value beyond the first 255 bytes. Further, system
-files written by some systems set this value to -1. In general, it is
+contribute to this value beyond the first 255 bytes. Further, some
+software always writes -1 or 0 in this field. In general, it is
unsafe for systems reading system files to rely upon this value.
@item int32 compression;
have value labels, but their value labels are recorded using a
different record type (@pxref{Long String Value Labels Record}).
+ReadStat (@pxref{File Header Record}) writes value labels that label a
+single value more than once. In more detail, it emits value labels
+whose values are longer than string variables' widths, that are
+identical in the actual width of the variable, e.g.@: labels for
+values @code{ABC123} and @code{ABC456} for a string variable with
+width 3. For files written by this software, PSPP ignores such
+labels.
+
The value label record has the following format:
@example
Record type. Always set to 6.
@item int32 n_lines;
-Number of lines of documents present.
+Number of lines of documents present. This should be greater than
+zero, but ReadStats writes system files with zero @code{n_lines}.
@item char lines[][80];
Document lines. The number of elements is defined by @code{n_lines}.