Computer Fundamental
Computer Tutorial

Magnetic Tape

Magnetic Tape

Magnetic tape is a plastic tape with magnetic coating. It is a storage medium on a large open reel or in a smaller cartridge or cassette (like a music cassette). Magnetic tapes are cheaper storage media. They are durable, can be written, erased, and re-written. Magnetic tapes are sequential access devices, which mean that the tape needs to rewind or move forward to the location where the requested data is positioned in the magnetic tape. Due to their sequential nature, magnetic tapes are not suitable for data files that need to be revised or updated often. They are generally used to store back-up data that is not frequently used or to transfer data from one system to other.

The working of magnetic tape

» Magnetic tape is divided horizontally into tracks (7 or 9) and vertically into frames. A frame stores one byte of data, and a track in a frame stores one bit. Data is stored in successive frames as a string with one data (byte) per frame.
» Data is recorded on tape in the form of blocks, where a block consists of a group of data also called as records. Each block is read continually. There is an Inter-Record Gap (IRG) between two blocks that provides time for the tape to be stopped and started between records.
» Magnetic tape is mounted on a magnetic tape drive for access. The basic magnetic tape drive mechanism consists of the supply reel, take-up reel, and the read/write head assembly. The magnetic tape moves on tape drive from the supply reel to take-up reel, with its magnetic coated side passing over the read/write head.
» Tapes are categorized based on their width - ¼ inch, ½ inch, etc.
» The storage capacity of the tape varies greatly. A 10–inch diameter reel of tape which is 2400 feet long can store up to 180 million characters.

The features of magnetic tape are —

• Inexpensive storage device
• Can store a large amount of data
• Easy to carry or transport
• Not suitable for random access data
• Slow access device
• Needs dust prevention, as dust can harm the tape
• Suitable for back-up storage or archiving