Slide 4.7: Magnetic tapes Slide 4.9: Magnetic tapes (cont.) Home

Magnetic Tapes (Cont.)

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A moving nine-track tape passes across a stationary record head. The recorded tracks are parallel to the edge of the tape and run the full length of the tape.

Tape is read and written on a tape drive (or “deck”) which winds the tape from one reel to the other causing it to move past a read/write head. 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. A tape has the following physical features:

• Since tapes are often read one block at a time and tapes can not stop or start instantly, blocks are separated by interblock gaps, which contain no information and are long enough to permit stopping and starting.
  
  
  
• The tape had reflective marks near its end which signaled beginning of tape (BOT) and end of tape (EOT) to the hardware.