Secondary Memory

Secondary memory is permanent storage type memory and is also non-volatile in nature. Secondary memory is required because RAM is volatile and with limited storage space. Secondary memory is cheaper than RAM. Secondary memory is available in different storage media devices.

Mainly two operations are performed in secondary storage devices:-

1. Read:-  Read operation read from memory.

                  (For exp. Playing music on a Smartphone)

2. Write: - Write operation, write data to memory.

                 (For exp. Downloading music into a Smartphone from the Internet)

Secondary Memory Storage Devices
Sequential Access Devices	Direct Access Devices
Magnetic Tapes	Magnetic Disk**  1. Floppy Disk 2. Hard Disk Optical Disc** 1. CD ROM  2. DVD Solid State** 1. Pen Drive           2. Memory Card

** To R/W (Read and Write) data secondary storage devices use different technologies. Some of the very commonly used technologies are Magnetic, Optical (Laser), Solid State (Chip)

Magnetic Tapes	Floppy Disk	Hard Disk
Optical and Solid-state Devices	CD, HDD File Systems FILE SYSTEMS	Memory Hierarchy

Memory Units

A bit is the smallest unit of memory.

8 Bits  =  1 Byte

4 Bits  = 1/2 Byte  (Nibble)

1024 Byte = 1 KB  (Kilo Byte)

1024 KB  =  1 MB  (Mega Byte)

1024 MB  = 1 GB   (Giga Byte)

1024 GB  = 1 TB    (Tera Byte)  

1 KB  = 2^10 Byte

1 MB = 2^20 Byte

1GB  = 2^30 Byte

1TB  = 2^40 Byte 

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