Magnetic Tape

Magnetic Tape is a secondary sequential storage media. Magnetic tape has also been used for years as an input or storage mediium and remains a choice today for high speed, large volume storage. Its data density is high, and it transfer rate is comparatively fast.The tape itself may be in a large reel or a smal cartidge or cassette. However packaged , the tape is usually similar to the kind used in tape recoder. It's a plastic ribbon that is coated on one side with iron oxide or some other material that can be magnetised. Tiny invisible spots representing data are recorded by electromagnetic pulses on the coated side of the tape.
Magnetic tape has a read head for reading the information stored on the tape,i.e. for transferring data from the tape into main storage . The tape moves past the read head at a speed of 200 inches per second.It is 0.5"wide and may be 50 ft.,100ft.,200ft.,400ft.,600ft.,1200ft.,2400ft.,long. There are 7 or 9 tracks depending upon the tape unit, which run the length of the tape. The data is coded so that the one character is recorded across the 7 or 9 tracks. The capcity of tapes having 9 tracks is 33% more than 7track system of the same length.Tape recording is sequential recording and if 10000th record is to be read, it has to read all 9999 records unnecessarily which is the one of its disadvantages. In case of floppy disk or hadr disk, the records are randomly acessed and time required to acess is less, compared to the tape unit
ADVANTAGE

• Magnetic tapes can be reused .
• Mass data storage in magnetic tape is cheaper.
• Data can be stored for long term retieval purpose.
• Data can be trasferred directiely into hard disk from magnetic tape.
  DISADVANTAGE
• Data cannot beread or written on magnetic tapes without electronics devices.
• Magnetic tapes are sensitive to dust, smoke, magnetic feild, heat, etc and data are damaged or lost.
• Since they are sequential strorage media, the access os data is relatively slow as the device has to read all the data before a point or access.