Question

How many types of secoundry memory with explain
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Answer 1

Answer:

Types of Secondary storage Devices in Computers are:

Magnetic tape

Magnetic disk and

Magnetic drum.

Magnetic tape:

• Tapes are used for recording and storing data for computer processing. It is plastic reel similar to long lengths of movie film. A tape is usually ½” wide and 2400 feet in length and it is coated with particles of ferric oxide on which data can be recorded magnetically.

• The process of reading and writing of data is carried out on a device called Tape Drive and the records on magnetic tape are stored in sequential order. For example: if the payroll file is to be stored on a magnetic tape, the records would likely to be stored in the sequence of employee numbers. Hence, magnetic tapes are referred to as sequential access device.

Magnetic disk:

• Magnetic disk is another type of secondary storage device known as random (direct) access as it permits direct accessing of data. An individual disk is a circular metal plate coated on both side by ferrous oxide material.

• Data is recorded in the form of magnetized spots on the tracks of the disk, a spot representing the presence by “1” and its absence by “0” enabling representing of data in binary form.

• The surface of the magnetic disk is divided into number of invisible concentric circles called “tracks” and these tracks are further subdivided into “sectors”, “blocks” etc. each its own unique addresses to facilitate the location of data and the Disk moves on a vertical rotating spindle.

• Reading /writing on the disks is accomplished by means of series of read/write heads which are placed close to the surfaces of the disks.

• It is good to know that data on the magnetic disk can be accessed again and again. It can also be recorded erasing the older information.

Magnetic drum:

• It is a metallic cylinder coated with a special magnetic alloy.

• Data is stored in this surface as minute magnetized spoke arranged in binary form in a series of parallel circular tracks.

• The drum rotates at a constant speed and data is recorded (or) retrieved by the read/write head. One for each track.

• The magnetic drum provides random access storage.

ADVANTAGES

Very fast access

Random access capability

Stored data is not destroyed until new data is written in the same location.

DISADVANTAGES

Drums cannot be removed from the unit and stored.

Storage capacity is limited.

Requires machine interpretation to read the information as it is not humanly readable.