Storage Devices are used to store data and information in form of bits and bytes in a computer.
Bits and Bytes are the data storage units.
1 Bit = "0" or "1" (Whatever we type in a computer, converted in form of 0 and 1, called binary or machine language )
1 Byte = 8 Bits (like - 11000101, 11111100, 10000001)
Let's understand some of the commonly used data storage units first.
1 Bit = "0" or "1"
1 Nibble = 4 Bits
1 Byte = 8 Bits or 2 Nibbles
1 Kilobyte (KB) = 1024 Bytes
1 Megabyte (MB) = 1024 KB
1 Gigabyte (GB) = 1024 MB
1 Terabyte (TB) = 1024 GB
1 Petabyte (PB) = 1024 TB
1 Exabyte (EB) = 1024 PB
1 Zettabyte (ZB) = 1024 EB
1 Yottabyte (YB) = 1024 ZB
The data or instructions that are given to the computer system by input devices are after processing kept into some storage media or memory units.
There are two types of computer memory : Primary memory and Secondary memory.
1. Primary Memory : It is main memory or internal memory of computer system. It is present on motherboard and has limited capacity. It is of two types:
RAM and ROM
RAM : RAM stands for Random Access Memory. It holds data while we are working on the computer and when computer is switched off the data is get erased. So RAM is a temporary or volatile memory unit. It is of two types :
SRAM and DRAM
SRAM : Full form of SRAM is Static RAM. Here data is stored using the state of six transistor memory cell. It is mostly used as a cache memory for the processor. It has lower access time so it is faster than DRAM. It requires a constant power supply. It has less storage capacity than DRAM.
DRAM : It stands of Dynamic RAM. It allows us to store each bit of data in a separate capacitor within storage circuit. It is standard memory unit of most of the desktop computers now a days. It regularly refreshes itself, so loses its data. It has higher access time, so slower than SRAM. It consumes less power than SRAM. It has small and simple internal circuitry than SRAM. Its cost is less than SRAM.
Some other kinds of RAM are FPM DRAM, SDR RAM, RD RAM, VRAM, EDO RAM, DDR SDRAM etc.
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| Different types of RAM |
EPROM (Erasable Programmable Read Only Memory) : Here program is erased using Ultra Violet light and then it is reprogrammed.
EEPROM (Electrically Erasable Programmable Read Only Memory): It can be erased and reprogrammed several times.
2. Secondary Memory : The secondary memory is used to store the data permanently. It is also called External memory. Its data is not erased even when the computer is switched off. We can store our works in a secondary memory. It is not an immediately accessible memory. There are many kinds of secondary memory, some of these are here :Hard Disk : A Hard disk drive is an electro-mechanical data storage medium that stores and retrieve digital data. It is composed of rigid, rapidly rotating platters made up of aluminium or glass coated with magnetic material. Platters having compartments to hold data. Here magnetic heads are arranged on a moving actuator arm. These heads are used to read and write data on the surface of the platter by moving of the actuator arm. The platters and actuator are delicate so covered under steel case to prevent damage to the disk under normal circumstances. It can store upto 5 TB (Terabyte) data.
Hard disk can be used in two ways Internal and External Hard disk.
An internal hard disk remains attached inside body (laptop) or in tower (Desktop). Where as an external hard disk is attached by USB cable to CPU port.
CD (Compact Disk) : A CD is a portable, external, optical disc data storage medium, can record, store or play back audio, video or other data. It can store 650 to 700 MB of data. It is a thin plate like structure can be inserted into a CD drive found in CPU or we can use CD player to listen to music or watch video or any other stored in it.
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| CD |
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| DVD |
Blue Ray Disk : It is also an optical rounded shape data storage medium like CD and DVD but can store upto 128 GB data. Because it uses blue laser to store data which allows information to be stored at a greater density.
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| Blue Ray Disc |
Pen Drive : Pen drive is also known as Flash drive, USB drive or Thumb drive is a portable, light weight and small sized data storage device. According to storage capabilities different types of pen drives available. It varies from 2 GB to 2 TB and its price increases with increasing capabilities of storing data. It can be attached by USB port with CPU. Now a days it is most popular for transferring data or keeping an easy backup of data because its so simple to keep it with you due to small size and light weight. Data storing, erasing or rewriting are very simple here. In comparison to a CD or DVD the prices are also less.  |
| Pen drive |
Cloud Storage : Cloud storage is a service to store data online. A user needs only an internet connection to access the data online. Using such kind of service to store data, there is no need to carry any storage device or no need to worry about the device in case it is lost or get damaged. One can access the data any where and any time only with a computer system and internet connection.
It is a virtual, secured and cost effective storage medium. The security and durability of data is very high. We can store upto 16 TB or more data, according to the service we are using. Data sharing is also very easy. Many services of cloud storage are available, some of these are Google Drive, One Drive, Dropbox.
Cloud Storage are available in four different models.
i. Public: Public cloud storage is a medium where an organisation stores data in service provider's data center that can be utilised by other companies.
ii. Private: Private cloud storage is a medium where where an organisation utilises its own server and data center to store data within its own network.
iii. Hybrid: Hybrid cloud storage is a mix of Public and Private cloud storage medium, where organisation decides which data should be stored in which cloud.
Here sesitive data or the data which have some restrictions are stored in privated cloud and less sesitive data stored in public cloud.
iv. Multicloud: Multicloud storage medium is where an organisation sets up more than one cloud models from more than one cloud service providers.
