MAGNETIC TAPE

Magnetic Tape 

• First kind of secondary memory 
• Lowest cost and slowest speed in memory hierarchy 
• Medium is flexible polyester tape coated with a magnetizable material 
• Packaged on reels or in cartridges 
• Data structured as a number of parallel tracks running lengthwise – parallel 
recording 
   o 9 tracks – 1 byte plus a parity bit
   o 18 tracks – 1 digital word
   o 36 tracks – 1 digital double word
• Modern systems use serial recording – data laid out as a sequence of bits along 
each track 
• Data can be read or written in contiguous blocks – called physical blocks 
• Interrecord gaps – gaps between blocks 
• Serpentine recording used with serial tapes 
    o Data recorded along one track at a time – full length of the tape
    o Each track is recorded in the opposite direction of the previous track

• The read-write head can read and write adjacent tracks simultaneously – 

increase speed 

• Data are still recorded serially along individual tracks, but blocks in sequence 

are stored on adjacent tracks

Tape drive 

• sequential access device – disk drive is a direct access device 

• if head is at record 1, then records 1 through N-1 are read in order to read 

record N 

• tape is in motion only during a read or write operation 

POSTED BY;

hazyanty shahira abd. halim