Computer Storage Devices
What is the computer storage device ?
Storage devices are used in the computers to store the data. These are the basic function and basic component of the computer because of computer can’t store the data without storage devices. Storage devices can be stored the data permanently or temporarily. They can be used to the computer as external or internal devices. Data to be processed, processed data, instructions for processing data are stored in storage devices. All computers are used a storage hierarchy. Different of memory types are use the computers.
Examples for the computer storage devices:
· Registers
· Random Access Memory (RAM)
· Read Only Memory (ROM)
· Hard disk (HDD)
· Cache memory
· Compact Disc (CD)
· Digital Versatile Disc (DVD)
· Blu — ray
· Flash memory (SSD — Solid State Drive)
· Magnetic tapes
· Complementary Metal Oxide Semiconductor (CMOS)
Usage of storage devices
User can get many advantages and disadvantages from storage devices. The followings are some of them.
· Some storage devices can store data in permanently. Some of them are temporarily.
· User can connect the external storage devices to the computer.
· Data transfer is easily by using storage devices.
· Storage devices are flexible to user.
· It helps to protect the important data.
· There are various kind of storage devices. Therefore user can select the suitable storage device for own tasks.
· Some storage devices are portable.
· Some storage devices can access data in high speed. Some of them are less speed.
· Many storage devices have more capacity. But some of them have less capacity.
· User can store any type of data in storage devices.
· Ability to retrieve stored data when needed.
· Data can be stored separately as required.
· It is possible to store the data required for a task over a period of time.
Types of storage
1. Primary storage
Primary memory is called as the main memory. This is the most important and main storage in the computer. Data and instructions that are currently use temporarily stored in the primary storage. That can exchange data directly with cpu. Primary storage has limited of capacity. This is the volatile memory. When the computer is deactivate or power gose out the data that stored in primary memory is erased. Primary memory can read and write data in very fast. Primary memory is made up of semiconductor materials.
Examples for primary storage:
· Random Access Memory (RAM)
· Read Only Memory (ROM)
· Cache memory
· Complementary Metal Oxide Semiconductor (CMOS)
RAM
The RAM can directly access any memory location. Therefore it called Random Access Memory. The data provided by input devices is temporary stored in RAM. RAM is high speed than hard disk. The data, information, instructions that regularly access by cpu are stored temporary in RAM. It takes the same amount of time to access the data, no matter where it is stored in RAM. RAM is connected in to the mother board.
The RAM is divided to three types.
I. Dynamic Random Access Memory (DRAM)
The Dynamic Random Access Memory is use for create the main memory. DRAM has ability to store very large amount of bits in a small physical space. Capacitors are used to create a DRAM. Charged capacitors are represent the 1 and uncharged capacitors are represent the 0. Stored power in capacitors is gradually decreases. Therefore the capacitors have to be charged regularly. Otherwise the stored data in the capacitors may be destroyed due to loss of power. The processor pauses the task for small time and charge the capacitors in the main memory. The processor operates every fifteen microseconds one time for it. DRAM is volatile memory.
Characteristics of DRAM:
· Ability to retain data for a short period of time.
· Once the data stored, the power to that data is gradually reduced.
· The capacitors must be recharged to prevent data loss.
· It does not require mush physical space to produce the required capacity to store large amounts of data.
II. Static Random Access Memory (SRAM)
Transistors are used for create SRAM. Therefore it is frequent charging is not required. The stored power does not decrease until the transistors receive uninterrupted power. It has ability to store data continuously until power is restored. SRAM is volatile memory. SRAM is not use to main memory and it use for registers and cache memory. It is speed and expensive than DRAM. SRAM is large in physically. Because it has to six transistors for one bit.
Characteristics of SRAM:
· Ability to retain data for a long period of time.
· It has not charging regularly.
· It has more physical space is required to produce even a small amount of storage capacity.
· It need to most of power.
III. Synchronous Dynamic Random Access Memory (SDRAM)
SDRAM have been in production since the 1970s. This is an advanced opportunity in RAM. SDRAM designed to be synchronous with processor speed.
Examples for SDRAM:- DDR, DDR2, DDR3, DDR4
ROM
ROM chip is use for store computer firmware. Computer BIOS program is stored in ROM chip. Data is inserted into the ROM chip during the manufacturing process. This type of ROM chip was first incorporated into motherboards. The stored data in ROM chip cannot be changed. ROM is a non-volatile memory. The data that stored in ROM chip can only be read. Therefore it called Read Only Memory. The processor is read the data in ROM chip.
There are several types of ROMs
I. PROM — Programmable Read Only Memory
Data can be written to PROM only once using a special tool. They cannot be erased.
II. EPROM — Erasable Programmable Read Only Memory
Data can be written and erased to EPROM using ultraviolet rays. For that this memory unit has to be connected to a special device. Can re- enter data by deleting the entered data.
III. EEPROM — Electronically Erasable Programmable Read Only Memory
Data can be written and read using electrical power. Data can be re- enter. EEPROM are used in today’s computer motherboard.
Advantages of EEPROM:
· Do not need to remove the EEPROM chip from the mounting location when overwriting the data.
· Data can be re- write a one part without delete all data.· Not need a special device for delete data.
Cache memory
This is called central processing unit memory (CPU memory). Cache memory is smaller than other memories. It’s speed is higher than other memories. It is work as an intermediary between CPU and primary memory. frequently used data is stored here. Cache memory is volatile memory. modern personal computers have three levels of cache memory. They are called L1 cache, L2 cache and L3 cache.
1. Secondary storage
Memory unit that can store data for long periods of time are called secondary storage. It is non- volatile memory. Secondary storage is called external storage. Some of secondary storage devices are must be connected to computer system internally. Some of them are connected externally.
Examples for secondary storage:- hard disk
2. Tertiary storage
Tertiary storage has a robotic mechanism. By it, inset and dismount removable mass storage media into a storage device. Tertiary storage is a comprehensive computer storage system. It is very slow. Therefore it is used to store non frequently used data. This is a primarily useful for extraordinarily large data stores, accessed without human operators.
Examples for tertiary storage:- Magnetic tape, Optical disc
3. Offline storage
Offline storage is called as disconnected storage. The every time you want to use data that stored in offline storage devices must be connected or inserted the devices in physically into a computer system. It is not built into the system. It is easy way to moving data. Offline storage devices are portable. They are compatible with range of systems. That can be used to create backups.
Examples for offline storage:- floppy disk, USB flash drive, memory card, zip diskette, hard disk, CD, DVD, SD cards
Types of computer storage devices
1. Magnetic storage devices
Magnetic storage devices are used magnetic technology for read and store data.
Examples for magnetic storage devices:-
· Hard disk
The hard disk was introduced by IBM in 1956. It is a main secondary storage device. A hard disk is in an all computers as a storage device. Vomiting technology is used in hard disk to store data and restore stored data to the main memory. Hard disk can read and write data in high speed. It has large amount of capacity. The hard disk is made up several parts. They are platter, spindle, head, actuator arm, power connection, IDE connector, actuator etc.
In the hard disk, one or few of platters are attached to the actuator arm. The platter is held in place and rotated by spindle. Data on the platter is read and write data on platter by head. The heads are moved by actuator. A platter is made up tracks. All platters have equal amount of tracks. A track is divided to parts. It is called sector. The amount of data that can write and read at once is called a block. When reading data, the head must be brought to the track firstly. The time taken for that is called seek time. After that, rotate the platter and bring the relevant sector to the head position. The time taken for that is called rotational delay. Then read data must be copy to main memory. The time taken for that is called transfer time. The most time consuming for seek time. If the correlated data is stored on the same track, the seek time is minimized.
Hard disk can be divided two options.
· Internal hard disk
· External hard disk
· Magnetic tape
Magnetic tape is made by magnetizing a plastic strip. It has a magnetical coated strip of plastic as data encoded. Magnetic tapes were originally made in Germany. These are used to store the data safely. It is used for backup data. Data write and read speed is slowly. But it has high capacity. Memory is accessed sequentially. Therefore memory cannot be accessed randomly. Magnetic tape is commonly used in server computers. These are less expensive.
Examples for magnetic tapes:- tape recorder, video recorder
· Floppy disk
Floppy disk is a soft magnetic disk. It is used magnetic technology to store data. It’s access speed is less than hard disk. It is less expensive. It has less storage capacity. A disk can store data up to 1.44 MB. Floppy disks have two common sizes as 5 ¼ and 3 ½. It is currently less in use. A main storage device used to carry data from the 80 and 90s. The data that stored floppy disk is destroy because of due to various environmental factors. Such as high temperature, dust.
· Zip diskette
Zip diskette is a hardware device. It is developed by Iomega. It functions like a standard 1.44 floppy drive. It capable to hold up to 100 MB of data or 250MB of data in new drives. It is less popular in present because of users needed larger storage capabilities.
1. Optical storage devices
Optical disc was introduced by Jems T. Rooshal in 1960. Optical storage devices are used digital technology to store data. It used laser rays to read and write data. Therefore it called optical storage devices. Can stored data easily in optical storage devices. The potential for data loss is minimal.
Examples for optical storage devices:- Compact Disc (CD), Digital Versatile Disc (DVD), Blue-ray Disc (BD)
1. Flash memory devices
Flash memory was introduced by Dr. Fujio Masuoka in 1980 who works at Toshiba cooperation. Flash memory speed is higher than hard disk. It has not mechanical parts. Therefore it called Solid State Drive (SSD). Data stored in any memory location can be accessed at the same time. This is non-volatile memory. Flash memory devices can be moved around. They used to read and write data. When replacing a computer’s hard drive with a flash drive, efficiency can be increased.
Examples for flash memory devices:-
· USB flash drive
It is a small device. It is a portable device and can be move around easily. USB flash drive must be connected to the computer via a USB port. It has the ability to handle data fast. Therefore flash drive is very popular storage device. Flash drives are available in sizes such as 2 GB to 256 GB. It is an easy way to transfer and store data. They are difference from optical and magnetic drives.
· Memory card
Memory card has the same activity as USB flash drive. It is an electronic flash disk. It changes the technology of connecting to a computer. It need the special reader device to read store data. That device called USB card reader. And also read the data in memory card by connected the device containing the memory card. It is very small and portable device. It is commonly used in consumer electronic devices such as digital cameras, mobile phones, MP3 players, computer game devices and other small portable devices.
Examples for memory card:- SD card (Secure Digital card)
2. Online cloud storage devices
Online cloud storage is a cloud computing model. That can be store data on the internet through a cloud computing provider. A online cloud computing provider is manages and operates data storage as a service.it is delivered on time, cost and capacity how user needed. User can join to the online cloud storage in anytime and anywhere. Not need to buy storage devices. Can store various kind of things in online cloud storage such as files, documents, videos, images, any objects etc.
Examples for cloud storage devices:- DropBox, iCloud, Google Drive, Microsoft One Drive, IDrive, Mega, Amazon Drive, pCloud
Most used storage devices
Some of storage devices are most used in present. Followings are some of them.
· USB flash drive
USB flash drive is most used as storage device. Followings are some reasons for it.
· This is small device.
· Available from different memory capacities.
· Easy to carry.
· Can be connected to the computer externally.
· Hard disk
Hard disk is most used as storage device. Followings are some reasons for it.
· Having an internal and external.
· It has large amount of capacity.
· Data read and write speed and access speed is high.
· Optical disc
Optical disc is most used as storage device. Followings are some reasons for it.
· Easy to carry.
· Disks that can write data once as well as disks that can write data again and again.
· Can store data easily.
· RAM
RAM is most used as storage device. Followings are some reasons for it.
· Being the main memory of the computer.
· Access speed is less.
· Small in physically.
· It is essential for data transfer in a computer.
· Cloud storage
Cloud storage is most used as storage device. Followings are some reasons for it.
· Can use easily.
· Can join from anytime and anywhere.
· Cost is less.
· The required number of devices is minimal.
Characteristics of computer storage devices
There are many characteristics of computer storage devices. Followings are some of them.
· Capacity
The volume of data that can be stored on a device is called capacity. There are storage devices of different capacities. The magnetic tapes have largest amount of capacity and the registers have the lowerst amount of capacity.
· Speed
Speed refers to the speed at which data is read and written in storage devices. This is depends on whether the device contains moving parts often. The registers have high speed to write and read data. But magnetic tapes have less speed to it.
· Access method
Access method is refers how to access the data that stored in storage devices. There are two access methods as random access and sequential access.
Random access is called direct access. It allows data to be retrieved from any location on the storage device by randomly. Therefore data access time is minimal. Virtually the most of storage devices are use random access. RAM, CD, DVD, USB flash drive, hard disk are example for random access devices.
Sequential access cannot be retrieve data randomly. It can retrieve the data only in the order which it was physically stored on the storage device. sequential access is less use in storage devices in present. Because it takes long amount of time to access data. Magnetic tape is example for it.
· Access speed
Access speed is refers the speed of access the data. Data access speeds on each type of devices may various. Access speed is high in random access storage devices. Sequential access storage devices have less access speed. The registers have the highest access speed and magnetic tapes have the lowerst access speed.
· Access time
Access time is means the time of take access data. Access time can be increased by storing correlated data in close proximity. The time that take to access data by random access storage devices is minimal. But sequential access storage devices take more amount of time for access data relatively.
· Portability
Portability is the ability to move devices around. Portable devices are lightweight and small. Most of storage devices are portable. CD, DVD, memory cards, USB flash drive are example for it.
· Cost
Cost is the price of purchasing the storage device. Some storage devices are very expensive and some of them are less amount of cost. Mostly the cost of storage devices depends on the cost per bit. The registers have the large amount of cost for bit. But magnetic tapes have less amount of cost per bit.
· Durability
Durability means ability to withstand physically movements. Some storage devices are need to be transport between other locations. Therefore they should have a high level of durability. If durability is high, damage to stored data is minimal. If durability is low, damage to stored data is too much relatively.
· Mutability
The mutability can be divided three parts.
1) Read/ write storage
Read/ write storage is called mutable storage. It has the ability to rewrite data at any time. Some computers have not read/ write storage for primary memory. They are useless for many purposes. The read/ write storage is use for secondary storage devices in modern computers today.
2) Read only storage
Read only storage can only be read. Data in stored to read only storage by manufacture. It can the data write once time and read many times. It is called immutable storage. They are used for offline and tertiary storage devices. ROM, CD-ROM, CD-R are example for it.
3) Slow write and fast read storage
This type of devices can be write data in several times. The writing process is slower than reading process in them. Flash memory, CD-RW are example for it.
· Reliability
Reliability of storage devices is depends on their durability. The security of the stored data should also be at a high level.
· Volatility
The volatility can be divide two parts.
1) Volatile memory
This type of memory devices are stored data temporarily. The data that stored these will be erased when the electrical power is turned off. The fastest memory technologies and devices are volatile in present. Primary storage is volatile because of it has to high speed. Registers, cache memory, RAM are examples for volatile memory.
2) Non-volatile memory
This type of memory devices are stored data permanently. Data is not erased even when there is no power. ROM, hard disk, CD, DVD, Blue-ray, magnetic tapes, flash memory are examples for non-volatile memory.
References
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