.th HT IV 2/9/75.sh NAMEht \*- RH-11/TU-16 magtape interface.sh DESCRIPTIONThe files.it "mt0, ..., mt7"refer to the DEC RH/TM/TU16 magtape.When opened for reading or writing,the tape is rewound.When closed, it is rewound;if it was open for writing, a double end-of-file is written first..s3A standard tape consists of aseries of 512 byte records terminated by a doubleend-of-file.To the extent possible, the system makesit possible, if inefficient, to treatthe tape like any other file.Seeks have their usual meaning and it is possibleto read or write a byte at a time.Writing in very small units is inadvisable,however, because it tends to create monstrous recordgaps..s3The.it mtfiles discussed above are usefulwhen it is desired to access the tape in a waycompatible with ordinary files.When foreign tapes are to be dealt with, and especiallywhen long records are to be read or written, the``raw'' interface is appropriate.The associated files are named.it "rmt0, ..., rmt7."Each.it reador.it writecall reads or writes the next record on the tape.In the write case the record has the same length as thebuffer given.During a read, the record size is passedback as the number of bytes read, provided it is no greaterthan the buffer size;if the record is long, an error is indicated.In raw tape I/O, the buffer must begin on a word boundaryand the count must be even.Seeks are ignored.An error is returned when a tape mark is read,but another read will fetch the first record of thenew tape file..sh FILES/dev/mt?,/dev/rmt?.sh "SEE ALSO"tp (I).sh BUGSRaw I/O doesnt work yet.The magtape system is supposed to be ableto take 64 drives.Such addressing has never been tried.These bugs will be fixed whenwe get more experience with this device..s3If any non-data error is encountered, it refuses to do anythingmore until closed.In raw I/O, there should be a wayto perform forward and backward record and file spacing andto write an EOF mark.