Storage Units(Primary & Secondary)

Storage units

The Devices that are used for storing data are known as storage devices. These devices can be Internal & External. These devices store & process data, Files, Software. All the software(Application, System software), Filestore on it.

There are two types of storage devices......................

• 1) Primary Storage Devices
• 2) Secondary Storage Devices  

Primary Storage Devices--

Storage Devices that store all the Software (Application, System software), File, Instruction, Data are known as Primary Storage Devices. It holds all the data while the file is on working.

There are some Primary Devices....................

• 1) RAM
• 2) ROM

RAM-- RAM stands for Random Access Memory. RAM is a volatile Primary memory. That is changeable. It consists of circuit chips It provides the space for the software for running. There are two main types of RAM: Dynamic RAM (DRAM) and Static RAM (SRAM). DRAM (pronounced DEE-RAM), is widely used as a computer's main memory. Each DRAM memory cell is made up of a transistor and a capacitor within an integrated circuit, and a data bit is stored in the capacitor.

DRAM-- Dynamic random-access memory is a type of random-access semiconductor memory that stores each bit of data in a memory cell consisting of a tiny capacitor and a transistor, both typically based on metal-oxide-semiconductor technology. The capacitor can either be charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1.

SRAM -- SRAM stands for the Static Random Access memory. Static random-access memory is a type of semiconductor random-access memory that uses bistable latching circuitry to store each bit. SRAM exhibits data remanence, but it is still volatile in the conventional sense that data is eventually lost when the memory is not powered.

Difference between DRAM & SRAM

DRAM	SRAM
It is composed of FLIP-FLOP	It is composed transistors and capacitors
Static RAM has got less memory capacity	Dynamic RAM has got comparatively more memory size
Data acess is slow	Data acess is fast

ROM--ROM stands for READ ONLY MEMORY. It is a non-volatile primary Memory. This is a Computer memory on which data has been prerecorded. Once the data has been written on the ROM chip, It cannot remove & can only read data stored in ROM that cannot be electronically modified after the manufacture of the memory device.

Rom has classified in few parts................

• A) PROM
• B) EPROM
• C) EEPROM  

PROM --PROM stands for Programmable Read-Only Memory. It is a form of digital memory where the setting of each bit is locked by a fuse or anti-fuse(fuses can also be used) It is one type of ROM (read-only memory). The data in them are permanent and cannot be changed.

EPROM-- EPROM stands for Erasable programmable read-only memory. It is a type of programmable read-only memory chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored data after a power supply has been turned off and back on is called non-volatile.

EEPROM-- EEPROM stands for Electrically Erasable programmable read-only memory. It is a user-modifiable read-only memory (ROM) that can be erased and reprogrammed (written to) repeatedly through the application of higher than normal electrical voltage. Unlike EPROM chips, EEPROMs do not need to be removed from the computer to be modified.

Secondary Storage Devices-- 

Secondary storage is non-volatile, long-term storage. It is used to keep programs and data indefinitely. Without secondary storage, all programs and data would be lost the moment the computer is switched off.

• A) Optical Disk
• B) Floppy Disk
• C) Pen Drive
• D) SD card
• E) Hard Disk--- 

1. a) Internal Hard Disk
2. b) External Hard Disk

Optical Disk--- This device can hold any type of data such as Data, Files, Movies, pictures, etc. It is covered with Plastic Coding.

Pen Drive--- Pen Drive is wildly in use. Because it is easy to carry it. The saving data & Copy, Paste is easy over it. It can also store data, files, movies, pictures,s, etc.

Hard Disk-- Hard disk is a piece of hard plastic that is fixed inside a computer and is used for storing data and programs permanently. A hard disk drive, hard disk, hard drive, or fixed disk is an electromechanical data storage device that stores and retrieves digital data using magnetic storage and one or more rigid rapidly rotating platters coated with magnetic material.

There are two types of hard disks we have………….

a) Internal-- An internal hard drive is a hard drive that resides inside the computer. Most computers come with a single internal hard drive, which includes the operating system and pre-installed applications. ... The internal hard drive is a key component of a computer since it stores the user's software and personal files. 

b) External-- It is an external hard drive is a device that you plug into a computer port. An external hard drive gives you more storage space to keep your data.

There are so many secondary storage devices are................

Floppy Disk— this is a storage device that is not in use nowadays. Its Storage Capacity is very Low. These have only 80 Kb storage. A floppy disk or floppy diskette is a type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined with a fabric that removes dust particles from the spinning disk. Floppy disks are read from and written to by a floppy disk drive.

SD Card--- SD cards are also in use. Working on it is also very easy. These can mostly use on Mobile phones. It is used for saving data externally.

Hard Disk—Hard Disk is the largest data storing device in your computer system. It holds all the data of your computer system. It holds all the programs, software (System software, Application Software).

Internal Hard Disk---- Internal Hard disks are present in your system. Which holds all the data, software, and all.

External Hard Disk--- External Hard Disk Are in plug And Play form. There is a USB port in your Cabinet (CPU). You just have to plug your hard disk into that just like a pen drive.

Cache memory

Cache memory is an extremely fast memory type that acts as a buffer between RAM and the CPU. It holds frequently requested data and instructions so that they are immediately available to the CPU when needed. Cache memory is used to reduce the average time to access data from the Main memory. It's not bad to clear your cached data now and then. Some refer to this data as “junk files,” meaning it just sits and piles up on your device. Clearing the cache helps keep things clean, but don't rely on it as a solid method for making new space.

Storage Unit

Unit of Storage	Representation
1 Bit(Binary Digit)	0 or 1
1 Byte	8 Bits
1 Kilobyte	1024 Bytes
1 Megabyte	1024 Kilobytes
1 Gigabyte	1024 Megabytes
1 Terabyte	1024 Gigabyte
1 Perabyte	1024 Terabyte
1 Exabyte	1024 Perabyte
1 Zettabyte	1024 Exabyte

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Author Vivek Singh Bhadauriya

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