Storage and Magnetic Devices

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Storage and Magnetic Devices

Storage Devices

A

storage device may hold information, process information, or both. A device

that only holds information is a recording medium. Devices that process information

(data storage equipment) may either access a separate portable (removable)

recording medium or a permanent component to store and retrieve information.

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Handicraft, sometimes more

precisely expressed as artisanal handicraft or handmade, is any of a wide

variety of types of work where useful and decorative objects are made

completely by hand or by using only simple tools. It is a traditional main

sector of craft, and applies to a wide range of creative and design activities that are related

to making things with one's hands and skill, including work with textiles,

moldable and rigid materials, paper, plant fibers, etc.

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Memory

card or flash card is an electronic flash memory data storage device used for storing

digital information. These are commonly used in many electronic devices,

including digital cameras, mobile phones, laptop computers, MP3 players andvideo game consoles, Tablets. Most of these can be diminutive, re-recordable,

and can retain data without power.

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ROM

cartridge, sometimes

referred to simply as a cartridge or cart, is a removable

enclosure containing read-only memory devices designed to be

connected to a consumer electronics device such as a home computer or games console. ROM cartridges can be used to load software such as video games, or other application programs.

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Hard

disk drive (HDD) is

a data storage device used for storing

and retrieving digital information using rapidly

rotating disks (platters) coated with magnetic material. An

HDD retains its data even when powered

off. Data is read in a random-accessmanner, meaning individual blocks of data can be

stored or retrieved in any order rather than sequentially. An HDD consists of one or more rigid

("hard") rapidly rotating disks (platters) with magnetic heads arranged on a moving actuator arm to read and write data to

the surfaces.

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Random-access

memory (RAM /ræm/) is a form of computer data storage. A random-access memory device allows data items to be read and written

in roughly the same amount of time regardless of the order in which data items

are accessed. In

contrast, with other direct-access data storage media such as hard disks, CD-RWs, DVD-RWs and the older drum memory, the time required to read and write data items varies

significantly depending on their physical locations on the recording medium,

due to mechanical limitations such as media rotation speeds and arm movement

delays.

Magnetic Devices

Magnetic

storage (or magnetic recording) is the storage of data on

a magnetized medium.

Magnetic storage uses different patterns of magnetization in

a magnetizable material to store data and is a form of non-volatile

memory. The information is accessed using one or more read/write

heads.

Analog

recording is based on the fact that remnant magnetization of a

given material depends on the magnitude of the applied field. The magnetic

material is normally in the form of tape, with the tape in its blank form being

initially demagnetized. When recording, the tape runs at a constant speed. The

writing head magnetizes the tape with current proportional to the signal. A

magnetization distribution is achieved along the magnetic tape. Finally, the

distribution of the magnetization can be read out, reproducing the original

signal. The magnetic tape is typically made by embedding magnetic particles in

a plastic binder on polyester film tape. The commonly used magnetic particles

are Iron oxide particles or Chromium oxide and metal particles with size of 0.5

micrometers. Analog recording was very popular in audio and video

recording. In the past 20 years, however, tape recording has been gradually

replaced by digital recording.

Instead of creating a magnetization distribution in analog recording, digital

recording only needs two stable magnetic states, which are the

+Ms and -Ms on the hysteresis loop. Examples of digital recording are floppy disks and hard disk

drives (HDDs). Digital recording has also been carried out on

tapes. However, HDDs offer superior capacities at reasonable prices; at the

time of writing (2014), consumer-grade HDDs offer data storage at about

3 GB/$.

Recording media on HDDs use a stack of thin films to store information and a

read/write head to read and write information to and from the media; various

developments have been carried out in the area of used materials.

Domain propagation memory is also called bubble memory.

The basic idea is to control domain wall motion in a magnetic medium that is

free of microstructure. Bubble refers to a stable cylindrical domain. Data is

then recorded by the presence/absence of a bubble domain. Domain propagation

memory has high insensitivity to shock and vibration, so its application is

usually in space and aeronautics.