+@item
+In BINARY mode, the data file is treated as a series of
+variable-length binary records. LRECL may be specified, but its value
+is ignored. The data for each record is both preceded and followed by
+a 32-bit signed integer in little-endian byte order that specifies the
+length of the record. (This redundancy permits records in these
+files to be efficiently read in reverse order, although PSPP always
+reads them in forward order.) The length does not include either
+integer.
+
+@item
+Mode 360 reads and writes files in formats first used for tapes in the
+1960s on IBM mainframe operating systems and still supported today by
+the modern successors of those operating systems. For more
+information, see @cite{OS/400 Tape and Diskette Device Programming},
+available on IBM's website.
+
+Alphanumeric data in mode 360 files are encoded in EBCDIC. PSPP
+translates EBCDIC to or from the host's native format as necessary on
+input or output, using an ASCII/EBCDIC translation that is one-to-one,
+so that a ``round trip'' from ASCII to EBCDIC back to ASCII, or vice
+versa, always yields exactly the original data.
+
+The RECFORM subcommand is required in mode 360. The precise file
+format depends on its setting:
+
+@table @asis
+@item F
+@itemx FIXED
+This record format is equivalent to IMAGE mode, except for EBCDIC
+translation.
+
+IBM documentation calls this @code{*F} (fixed-length, deblocked)
+format.
+
+@item V
+@itemx VARIABLE
+The file comprises a sequence of zero or more variable-length blocks.
+Each block begins with a 4-byte @dfn{block descriptor word} (BDW).
+The first two bytes of the BDW are an unsigned integer in big-endian
+byte order that specifies the length of the block, including the BDW
+itself. The other two bytes of the BDW are ignored on input and
+written as zeros on output.
+
+Following the BDW, the remainder of each block is a sequence of one or
+more variable-length records, each of which in turn begins with a
+4-byte @dfn{record descriptor word} (RDW) that has the same format as
+the BDW. Following the RDW, the remainder of each record is the
+record data.
+
+The maximum length of a record in VARIABLE mode is 65,527 bytes:
+65,535 bytes (the maximum value of a 16-bit unsigned integer), minus 4
+bytes for the BDW, minus 4 bytes for the RDW.
+
+In mode VARIABLE, LRECL specifies a maximum, not a fixed, record
+length, in bytes. The default is 8,192.
+
+IBM documentation calls this @code{*VB} (variable-length, blocked,
+unspanned) format.
+
+@item VS
+@itemx SPANNED
+The file format is like that of VARIABLE mode, except that logical
+records may be split among multiple physical records (called
+@dfn{segments}) or blocks. In SPANNED mode, the third byte of each
+RDW is called the segment control character (SCC). Odd SCC values
+cause the segment to be appended to a record buffer maintained in
+memory; even values also append the segment and then flush its
+contents to the input procedure. Canonically, SCC value 0 designates
+a record not spanned among multiple segments, and values 1 through 3
+designate the first segment, the last segment, or an intermediate
+segment, respectively, within a multi-segment record. The record
+buffer is also flushed at end of file regardless of the final record's
+SCC.
+
+The maximum length of a logical record in VARIABLE mode is limited
+only by memory available to PSPP. Segments are limited to 65,527
+bytes, as in VARIABLE mode.
+
+This format is similar to what IBM documentation call @code{*VS}
+(variable-length, deblocked, spanned) format.
+@end table
+
+In mode 360, fields of type A that extend beyond the end of a record
+read from disk are padded with spaces in the host's native character
+set, which are then translated from EBCDIC to the native character
+set. Thus, when the host's native character set is based on ASCII,
+these fields are effectively padded with character @code{X'80'}. This
+wart is implemented for compatibility.
+
+@item
+SCRATCH mode is a PSPP extension that designates the file handle as a
+scratch file handle.
projects / pspp-builds.git / blobdiff