SPSS® 12.0 Command Syntax Reference

EXPORT 531
• Tape density—200, 556, 800, 1600, or 6250 bits per inch (BPI).
• Parity—even or odd. This must be known only when writing a 7-track tape.
• Tape labeling—labeled or unlabeled. Check whether the site can use tape labels. Also
make sure that the site has the ability to read multivolume tape files if the file being
written uses more than one tape.
• Blocksize—the maximum blocksize the receiving computer can accept.
A tape written with the following characteristics can be read by most computers: 9 track,
1600 BPI, unlabeled, and a blocksize of 3200 characters. However, there is no guarantee that
a tape written with these characteristics can be read successfully. The best policy is to know
the requirements of the receiving computer ahead of time.
The following advice may help ensure successful file transfers by magnetic tape:
• Unless you are certain that the receiving computer can read labels, prepare an unlabeled
tape.
• Make sure the record length of 80 is not changed.
• Do not use a separate character translation program, especially ASCII/EBCDIC translations.
EXPORT/IMPORT takes care of this for you.
• Make sure the same blocking factor is used when writing and reading the tape. A blocksize
of 3200 is frequently a good choice.
• If possible, write the portable file directly to tape to avoid possible interference from copy
programs. Read the file directly from the tape for the same reason.
• Use the INFO LOCAL command to find out about using the program on your particular
computer and operating system. INFO LOCAL generally includes additional information
about reading and writing portable files.
Communications Programs
Transmission of a portable file by a communications program may not be possible if the
program misinterprets any characters in the file as control characters (for example, as a line feed,
carriage return, or end of transmission). This can be prevented by specifying TYPE=COMM on
EXPORT. This specification replaces each control character with the character 0. The affected
control characters are in positions 0–60 of the IMPORT/EXPORT character set (see Appendix B).
The line length that the communications program uses must be set to 80 to match the
80-character record length of portable files. A transmitted file must be checked for blank
lines or special characters inserted by the communications program. These must be edited
out prior to reading the file with the IMPORT command.
Character Translation
Portable files are character files, not binary files, and they have 80-character records so they
can be transmitted over data links. A receiving computer may not use the same character set
as the computer where the portable file was written. When it imports a portable file, the
program translates characters in the file to the character set used by the receiving computer.
Depending on the character set in use, some characters in labels and in string data may be