+@menu
+* System File Record Structure::
+* File Header Record::
+* Variable Record::
+* Value Labels Records::
+* Document Record::
+* Machine Integer Info Record::
+* Machine Floating-Point Info Record::
+* Multiple Response Sets Records::
+* Extra Product Info Record::
+* Variable Display Parameter Record::
+* Long Variable Names Record::
+* Very Long String Record::
+* Character Encoding Record::
+* Long String Value Labels Record::
+* Long String Missing Values Record::
+* Data File and Variable Attributes Records::
+* Extended Number of Cases Record::
+* Other Informational Records::
+* Dictionary Termination Record::
+* Data Record::
+@end menu
+
+@node System File Record Structure
+@section System File Record Structure
+
+System files are divided into records with the following format:
+
+@example
+int32 type;
+char data[];
+@end example
+
+This header does not identify the length of the @code{data} or any
+information about what it contains, so the system file reader must
+understand the format of @code{data} based on @code{type}. However,
+records with type 7, called @dfn{extension records}, have a stricter
+format:
+
+@example
+int32 type;
+int32 subtype;
+int32 size;
+int32 count;
+char data[size * count];
+@end example
+
+@table @code
+@item int32 rec_type;
+Record type. Always set to 7.
+
+@item int32 subtype;
+Record subtype. This value identifies a particular kind of extension
+record.