What are computer storage devices and computer memory unit also describe the various storage devices

What are computer storage devices and computer memory unit also describe the various storage devices


Overview – Meaning and Definition of Computer Memory Unit, types of storage devices, meaning of primary storage/primary storage devices/ random access memory/ secondary storage devices/ floppy disc drive/ hard drive/ magnetic tape/ diskettes/ compact disc/ digital versatile disc and USB flesh drives

Computer Memory Unit:

What is Memory Unit of Computer?

A data storage device is a device for recording (storing) information (data).   Recording  can be  done  using  virtually  any  form  of energy, spanning from manual muscle power in handwriting, to acoustic vibrations in phonographic recording, to electromagnetic energy modulating magnetic tape and optical discs.A storage device is a hardware device capable of storing information. There     are two types of storage devices used in computers; a primary storage device such as computer RAM and a secondary storage device such as a computer hard disk drive. 


Hierarchy of Storage:

Types and Classification of Storage Devices:

Primary Storage :- (Meaning of Primary Storage) - Primary storage (or main memory or internal memory), often referred to simply as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in uniform manner.

Primary Storage Device :- Also known as internal memory and main memory, primary storage is a storage location that holds memory for short periods of times while the computer is on. For example, computer RAM and cache are both examples of a primary storage device. This type of storage is the fastest type of memory in your computer and is used to store data while it's being used. For example, when you open a program data is moved from the secondary storage into the primary storage.

Random Access Memory :- RAM, also known as main memory or system memory, is a term commonly used to describe the memory within a computer.Unlike ROM, RAM is a volatile memory and requires power; if power is lost, all data is also lost. Below is an example image of a 512MB DIMM memory stick.Over the evolution of computers there has been several different types of RAM used in computer. Some of the more common examples are: DIMM, RIMM, SIMM, SO-DIMM, and SOO-RIMM. 

Secondary storage device:- Also known as external memory and auxiliary storage, secondary storage is a storage medium that holds information until it is deleted or overwritten regardless if the computer has power. For example, a floppy disk drive and hard disk drive are both good examples of secondary storage devices. As can be seen by the below picture there are three  different types of storage on a computer, although primary storage is accessed much faster than secondary storage because of the price and size limitations secondary storage is used with today's computers to store all your programs and your personal data. Finally , although off-line storage could be considered secondary storage, we've separated these into their own category because these types of media can be easily removed from the computer and stored elsewhere. Some other examples of secondary storage technologies are: flash memory (e.g. USB flash drives or keys), floppy disks, magnetic tape, paper tape, punched cards, standalone RAM disks, and Iomega Zip drives.



Floppy Disk Drive :- A Floppy Disk Drive, or FDD for short, is a computer disk drive that enables a user to easily save data to removable diskettes. Although 8" disk drives made available in 1971 were the first real disk drives, the first widely used an floppy disk drives were the 5 1/4" floppy disk drives, which were later replaced with 3 1/2" floppy disk drives. However, today because of the limited capacity and eliability of floppy diskettes many computers no longer come equipped with floppy disk drives and are being replaced with CD-R and other writable disc drives and flash drives.
Above is an example of each of the floppy drives.
  
Hard drive :-The computer's main storage media device used to permanently store  all data on the computer.  Also  referred to as a hard disk drive or abbreviated as HD or HDD, the hard drive was first introduced on September 13, 1956 and consists of one or more hard disk platters inside of air sealed casing. Most hard drives are permanently stored in an internal drive bay at the front of the computer and are connected with either ATA, SCSI, or a SATA cable and power cable. Below is an illustration of the inside of a hard disk drive.
  
Magnetic tape :- Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders. A device that stores computer data on magnetic tape is a tape  drive. Magnetic tape revolutionized broadcast and recording. When all radio was live, it allowed programming to be prerecorded. At a time when  gramophone records were recorded in one take, it allowed recordings in multiple parts, which mixed and edited with tolerable loss in quality. It is a key technology in early computer development, allowing unparalleled amounts of data to be mechanically created, stored for long periods, and to be rapidly accessed.


Diskettes :- You can use the diskette to store small amounts of information. According to Mediastoragedevices.com, a widely used diskette has a capacity of 1.44 Mb. It records data as magnetized spots on tracks on its surface. Diskettes are portable, allowing you to move data from one computer to another. You have to ensure that you do not store data on the diskette for long periods, because as the magnetic field weakens, you risk losing your stored data. 

Compact Disc:- Stands for "Compact Disc." CDs are circular discs that are 4.75 in (12 cm) in diameter. The CD standard was proposed by Sony and Philips in 1980 and the technology was introduced to the U.S. market in 1983. CDs can hold up to 700 MB of data or 80 minutes of audio. The data on a CD is stored as small notches on the disc and is read by a laser from an optical drive. The drives translate the notches (which represent 1's and 0's) into usable data. The first CDs were audio CDs, which eventually replaced audio tapes (which earlier replaced records). Audio CDs have the advantage of allowing the user to jump to different places on the disc. CDs can also be

listened to an unlimited number of times without losing quality. Audio tapes can start to lose quality after listening to them as few as ten times. This is because the laser that reads the data on a CD doesn't put pressure on the disc, whereas the play heads on a tape deck slowly wear away the magnetic strip on the tape. 

Digital Versatile Disc :- Stands for "Digital Versatile Disc." It can also stand for "Digital Video Disc," but with the mulitple uses of DVDs, the term "Digital Versatile Disc" is more correct. Yep, the technology naming people just love to confuse us. A DVD is a high-capacity optical disc that looks like a CD, but can store much more information. While a CD can store 650 to 700 MB of data, a single-layer, single-sided DVD can store 4.7 GB of data. This enables massive computer applications and full-length movies to be stored on a single DVD. The advanced DVD formats are even more amazing. There is a twolayer standard that doubles the single-sided capacity to 8.5 GB. These disks can also be double-sided, ramping up the maximum storage on a single disc to 17 GB. That's 26 times more data than a CD can hold! To be able to read DVDs in your computer you'll need a DVD-ROM drive. Fortunately, DVD players can also read CDs. To play DVD movies on your computer, you'll need to have a graphics card with a DVD-decoder, which most computers now have.


USB Flash Drives:- The convenience of storing and transferring data in a device that is portable and has a large capacity comes with the USB flash drive. You only have to connect it to the computer through the USB port and transfer data from the computer to the flash drive and vice versa. It comes in various sizes (usually in gigabytes) to suit your usage needs and you can carry it in your pocket or wallet or on your key chain. Apart from being fast in uploading data, it also gives you the option of modifying the stored data by either erasing or rewriting according to your requirements.


  

Short exam hand made lecture notes of computer ICT practical file basics and Computer storage devices lecture notes

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