X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=doc%2Fdev%2Fsystem-file-format.texi;h=b8670681d9e3789a9803d1e31eae56d54ac32cc7;hb=8c7010202f34d6648359603f6490ce2fe4084b6e;hp=116fa6f787445fb5931e9ae2dafe87eb97782988;hpb=5dbf5abcbed01f04422d4dead1c0ae0bb7efde4f;p=pspp

diff --git a/doc/dev/system-file-format.texi b/doc/dev/system-file-format.texi
index 116fa6f787..b8670681d9 100644
--- a/doc/dev/system-file-format.texi
+++ b/doc/dev/system-file-format.texi
@@ -1,12 +1,25 @@
+@c PSPP - a program for statistical analysis.
+@c Copyright (C) 2019 Free Software Foundation, Inc.
+@c Permission is granted to copy, distribute and/or modify this document
+@c under the terms of the GNU Free Documentation License, Version 1.3
+@c or any later version published by the Free Software Foundation;
+@c with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
+@c A copy of the license is included in the section entitled "GNU
+@c Free Documentation License".
+@c
+
 @node System File Format
-@appendix System File Format
+@chapter System File Format
 
-A system file encapsulates a set of cases and dictionary information
-that describes how they may be interpreted.  This chapter describes
-the format of a system file.
+An SPSS system file holds a set of cases and dictionary information
+that describes how they may be interpreted.  The system file format
+dates back 40+ years and has evolved greatly over that time to support
+new features, but in a way to facilitate interchange between even the
+oldest and newest versions of software.  This chapter describes the
+system file format.
 
 System files use four data types: 8-bit characters, 32-bit integers,
-64-bit integers, 
+64-bit integers,
 and 64-bit floating points, called here @code{char}, @code{int32},
 @code{int64}, and
 @code{flt64}, respectively.  Data is not necessarily aligned on a word
@@ -316,10 +329,10 @@ so readers should take care to parse dummy variable records in the
 same way as other variable records.
 
 @anchor{Dictionary Index}
-The @dfn{dictionary index} of a variable is its offset in the set of
+The @dfn{dictionary index} of a variable is a 1-based offset in the set of
 variable records, including dummy variable records for long string
-variables.  The first variable record has a dictionary index of 0, the
-second has a dictionary index of 1, and so on.
+variables.  The first variable record has a dictionary index of 1, the
+second has a dictionary index of 2, and so on.
 
 The system file format does not directly support string variables
 wider than 255 bytes.  Such very long string variables are represented
@@ -514,6 +527,10 @@ Format types are defined as follows:
 @tab @code{EDATE}
 @item 39
 @tab @code{SDATE}
+@item 40
+@tab @code{MTIME}
+@item 41
+@tab @code{YMDHMS}
 @end multitable
 @end quotation
 
@@ -544,7 +561,7 @@ The value label record has the following format:
 int32               rec_type;
 int32               label_count;
 
-/* @r{Repeated @code{label_cnt} times}. */
+/* @r{Repeated @code{n_label} times}. */
 char                value[8];
 char                label_len;
 char                label[];
@@ -596,7 +613,7 @@ Number of variables that the associated value labels from the value
 label record are to be applied.
 
 @item int32 vars[];
-A list of dictionary indexes of variables to which to apply the value
+A list of 1-based dictionary indexes of variables to which to apply the value
 labels (@pxref{Dictionary Index}).  There are @code{var_count}
 elements.
 
@@ -987,18 +1004,24 @@ members are as follows:
 
 @table @code
 @item int32 measure;
-The measurement type of the variable:
+The measurement level of the variable:
 @table @asis
+@item 0
+Unknown
 @item 1
-Nominal Scale
+Nominal
 @item 2
-Ordinal Scale
+Ordinal
 @item 3
-Continuous Scale
+Scale
 @end table
 
-SPSS sometimes writes a @code{measure} of 0.  PSPP interprets this as
-nominal scale.
+An ``unknown'' @code{measure} of 0 means that the variable was created
+in some way that doesn't make the measurement level clear, e.g.@: with
+a @code{COMPUTE} transformation.  PSPP sets the measurement level the
+first time it reads the data using the rules documented in
+@ref{Measurement Level,,,pspp, PSPP Users Guide}, so this should
+rarely appear.
 
 @item int32 width;
 The width of the display column for the variable in characters.
@@ -1504,7 +1527,8 @@ the following believed meanings:
 
 @table @asis
 @item 5
-A set of grouped variables (according to Aapi H@"am@"al@"ainen).
+A named variable set for use in the GUI (according to Aapi
+H@"am@"al@"ainen).
 
 @item 6
 Date info, probably related to USE (according to Aapi H@"am@"al@"ainen).
@@ -1637,7 +1661,7 @@ The number of bytes in the ZLIB data trailer.  This and the previous
 field sum to the size of the system file in bytes.
 @end table
 
-The data header is followed by @code{(ztrailer_ofs - 24) / 24} ZLIB
+The data header is followed by @code{(ztrailer_len - 24) / 24} ZLIB
 compressed data blocks.  Each ZLIB compressed data block begins with a
 ZLIB header as specified in RFC@tie{}1950, e.g.@: hex bytes @code{78
 01} (the only header yet observed in practice).  Each block
@@ -1674,7 +1698,7 @@ been observed so far.
 
 @item int32 n_blocks;
 The number of ZLIB compressed data blocks, always exactly
-@code{(ztrailer_ofs - 24) / 24}.
+@code{(ztrailer_len - 24) / 24}.
 @end table
 
 The fixed header is followed by @code{n_blocks} 24-byte ZLIB data