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Different units of storage of data are:
No. of bits/bytes Unit
8 Bits 1 Byte
1024 Bytes 1 Kilobyte
1024 Kilobytes (KB) 1 Megabyte
1024 Megabytes (MB) 1 Gigabyte
1024 Gigabytes (GB) 1 Terabyte
1024 Terabytes (TB) 1 Petabyte
1024 Petabytes (PB) 1 Exabyte
1024 Exabytes (EB) 1 Zettabyte
1024 Zettabytes (ZB) 1 Yottabyte
1024 Yottabytes (YB) 1 Brontobyte
1024 Brontobytes (BB) 1 Geopbyte
Secondary Memory / Auxiliary Memory
Secondary memory refers to the permanent storage of data. During the operation of a computer, the currently
used data lies in the temporary memory. It may be lost if the computer is suddenly switched ‘OFF’. For this
purpose, secondary memory is required, as it provides the necessary backup and storage of instructions or
data that are permanent & can be retrieved back as and when required. It is also known as backup memory. It
has a higher storage capacity than the primary storage/memory. There are various types of secondary storage
devices. Some of them are:
Magnetic Disks: Magnetic Disks are storage devices that are made up of several disks coated with magnetic
material.
The surface of each disk is marked with invisible circular tracks. The data is stored in the form of magnetic
spots on a disk.
Hard Disk: It is the most widely used internal storage magnetic disk. It is made a higher of spindles of smooth
metallic plates coated with a thin layer of magnetic material. Each plate of a hard disk is called a platter. Each
platter has two (read/write) heads, one on each side. Over the years, hard disks have been available in various
storage capacities. E.g. 20 MB in earlier days to 160 GB, 320 GB, 500 GB, 1 TB, 5 TB, 6 TB, 12 TB, 16 TB and
more in recent times.
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