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Nearly all recording tape is of this type, whether used for
video with a video cassette recorder, audio storage ( reel-to-reel tape, compact audio cassette, digital audio tape (DAT), digital linear tape (DLT) and other formats including 8-track cartridges) or general purpose digital data storage using a computer (specialized tape formats, as well as the above-mentioned compact audio cassette, used with home computers of the 1980s, and DAT, used for backup in workstation installations of the 1990s).Magneto-optical and optical tape storage products have been developed using many of the same concepts as magnetic storage, but have achieved little commercial success.
Magnetic tape is a common video storage medium, especially for recording. At home, VHSThe Video Home System better known by its acronym VHS is the recording and playing standard for video cassette recorders (VCRs), developed by JVC and launched in 1976. It became a standard format for consumer recording and viewing in the 1980s after compe cassettes are omnipresent while DVDV is a video format launched in 1996, which encodes video onto tape in digital format with intraframe compression, making it straightforward to transfer the video onto computer for editing. DV tapes come in two formats: MiniDV and DV. They record digital has become the standard for consumer camcorders, and at TV studios digital video cassettes such as DVCPRODVCPRO DVCPRO 50 and DVCPRO HD refer to digital videotape formats using the DV codec, and devised by Panasonic. You may also see in older Panasonic literature references to 'DVCPRO 25' and 'DVCPRO 100'. These were the original names for DVCPRO and DVCPRO, DVCAMDVCAM is Sony's professional implementation of the DV standard, using 15 micrometre tracks instead of DV's 10 micrometre tracks. DVCAM decks can play back DV tapes, though the reverse is not true. Video storage. and Digital BetacamDigital Betacam is a video tape format created by Sony and launched in 1993 for professional television broadcasters. It represents a second generation family of equipment beyond Sony's widely used analog system, Betacam SP. It costs significantly less th have been common for years.
Magnetic tape was first used to record data in 1951 on the Mauchly-Eckert UNIVAC IThe UNIVAC I UNIV ersal A utomatic C omputer I was the first commercial computer made in the United States. It was designed by J. Presper Eckert and John Mauchly, the men behind the first American electronic computer, the ENIAC. During the years before su. The recording medium was a thin band of solid steel. Recording density was 128 characters per inch at a linear speed of 100 ips, yielding a data rate of 12800 characters per second.
A tape drive (or "transport" or "deck") uses precisely-controlled motors to wind the tape from one reel to the other, passing a read/write head as it does. Early tape had seven parallel tracks of data along the length of the tape allowing six bit characters plus parity written across the tape. A typical recording density was 556 characters per inch. The tape had reflective marks near its end which signaled beginning of tape (BOT) and end of tape (EOT) to the hardware. Since then, a multitude of tape formats have been used, but common features emerge.
In a typical format, data is written to tape in blocks with inter-block gaps between them, and each block is written in a single operation with the tape running continuously during the write.
However, since the rate at which data is written or read to the tape drive is not deterministic, a tape drive usually has to cope with a difference between the rate at which data goes on and off the tape and the rate at which data is supplied or demanded by its host.
Various methods have been used alone and in combination to cope with this difference. A large memory buffer can be used to queue the data. The tape drive can be stopped, backed up, and restarted. The host can assist this process by choosing appropriate block sizes to send to the tape drive.
There is a complex tradeoff between block size, the size of the data buffer in the record/playback deck, the percentage of tape lost on inter-block gaps, and read/write throughput.
Tape has quite a long data latency for random accesses since the deck must wind an average of 1/3 the tape length to move from one arbitrary data block to another. Most tape systems attempt to alleviate the intrinsic long latency using either indexing, whereby a separate lookup table is maintained which gives the physical tape location for a given data block number, or marking, whereby a tape mark that can be detected while winding the tape at high speed is written to the tape.
Most tape drives now include some kind of data compression. There are several algorithms which provide similar results: LZ (Most), IDRC (Exabyte), ALDC (IBM, QIC) and DLZ1 (DLT). The actual compression algorithms used are not the most effective known today, and better results can usually be obtained by turning off the compression built into the device and using a software compression program instead.
Tape remains a viable alternative to disk due to its higher bit density and lower cost per bit. Tape has historically offered enough advantage in these two areas above disk storage to make it a viable product. The recent vigorous innovation in disk storage density and price, coupled with less-vigorous innovation in tape storage, has reduced the viability of tape storage products.
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