Magnetic Tape
Magnetic
tape is one of the most popular storage mediums for large data that are
sequentially accessed and processed. Different types of tapes are available
like ½ inch or ¼ inch wide plastic tape. The tape ribbon itself is stored in
reels similar to the tape used on computer tape recorder except that it is of
high durable.
Like audio
tape, computer tape can be erased and reused indefinitely. Old data on a tape
an automatically erased as new data are recorded in the same area.
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Figure: Magnetic Tape read/write head |
The information is recorded on the tape with the help of read/write head. It magnetises or non-magnetises tiny invisible spots (representing 1’s and 0’s) on the tape as shown in diagram.
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Figure: Cross section of Magnetic Tape |
Seven or nine bits are recorded in parallel across the width of the tap. A separate read/write head is provided for each bit position on the tape, so that all bits of characters can be read or written in parallel.
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| Figure: Layout of Magnetic Tape |
Data on
the tape are organized in the form of records separated by gaps,
as shown in next diagram. A set of related records called a file.
A file mark is used to identify beginning of the file. The file
mark is a special single or multiple character record. The record following the
file mark (first record) can be used as a header or identifier
for this file.
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