Beginning of next file rewind fully rewinds the tape

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Unformatted text preview: When processing is complete, the tape is removed from the tape drive for off-line storage; that is, it is stored away from the computer system and data on it are not accessible to the computer system until it is loaded again on the tape drive for processing. Like audio or video tape, the magnetic tape, used in computer systems can also be erased and reused indefinitely. Old data on a tape are automatically erased as new data are recorded in the same area. Tape Controller A magnetic tape has to be mounted on a tape drive before it can be used for reading or writing of information. A tape drive is connected to and controlled by a tape controller which interprets the commands for operating the tape drive. A typical set of commands supported by a tape controller are: Read reads one block of data Write writes one block of data Write tape header label used to update the contents of tape header label Erase tape erases the data recorded on a tape Back space one block rewinds the tape to the beginning of previous block Forward space one block forwards the tape to the beginning of next block Back space one file rewinds the tape to the beginning of previous file Forward space one file forwards the tape to the beginning of next file Rewind fully rewinds the tape Unload releases the tape drive's grip so that the tape spool can be unmounted from the tape drive Types of Magnetic Tapes The data recording density and data transfer rate of magnetic tapes depend to a large extent on the data organization and principles of operation of various types of magnetic tapes and their tape drives. The commonly used ones are: 1. ½ - inch tape reel 2. ½ -inch tape cartridge 3. ¼ inch streamer tape 4. 4-mm digital audio tape (DAT) They are described below. Half-inch Tape Reel A magnetic tape reel uses 14 inch tape ribbon stored on a tape reel (see Figure 8.7). The magnetic tape drive of a tape reel is shown in Figure 8.8. The tape on a reel moves through a tape drive in much the same way as a video tape moves through a movie projector. During processing, the tape moves from a supply reel to a take-up reel via two vacuum channels and through a read/write head assembly. The rea...
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This document was uploaded on 04/07/2014.

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