2. • Used to store large amount of data.
• Same technology of Magnetic Disk.
• Magnetic film is deposited on a very thin 0.5
or 0.25 inch wide plastic tape.
• 7 or 9 bits are recorded in parallel across the
width of tape.
• A separate Read/Write head is provided for
each bit position on the tape, in order to read
or write all bits of a character parallel.
3.
4.
5. File
7 or
9
bits
Record Record
File Mark Gap
Organization of Data on Magnetic Tape
6. • Data on the tape are organized in the form of records
separated by gaps.
• Tape motion is stopped when a record gap is under
the Read/Write heads.
• Group of related records called a FILE. Which is used
to help users organize large accounts of data.
• The beginning of a file is identified by a file mark
which is a special single or multiple character record,
usually proceeded by a gap longer than the inter
record gap.
7. • The first record following a file mark can be
used as a header or Identifier for this file
allowing the user to search a tape containing
a large number of files for a particular file.
8. Control Commands by a Controller
• Rewind Tape
• Rewind and unload tape.
• Erase Tape.
• Write tape mark.
• Forward space one record.
• Backspace one record.
• Forward space one file
• Backspace one file.
9. Method of formatting and using
tapes
Two methods:
1. The records are variable in length.
Advantages:
Tape can be used efficiently.
Disadvantages:
Not permit updating & overwriting
10. 2. The records are of Fixed Length
Advantages:
Possible to update records
Applications of Magnetic tapes:
storage of data.
back up information.
11. Cartridge Tape system
• 8mm video format tape housed in a cassette.
• Capacity 2-5 GB
• Data transfer rate--? Few hundred KBPS
• Read/Write helical scan system
