The Magnetic Storage Devices Computer Science Essay

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The magnetic storage devices have been playing an important role in our life. Magnetic storage is a device to store data and its non-volatile memory. Magnetic storage can be classified as either sequential access memory or random access memory. Most common used magnetic storage is Hard Drive, Floppy Disk, MRAM, Magnetic Stripe Card, Drum Memory, and many more. There are many magnetic storage was invented but in this scrapbook is only wrote about the Hard Drive, MRAM, Floppy Disk, and the Magnetic Stripe Card only.

Hard disk drive is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surface, it commonly referred to as hard drive, hard disk, or fixed disk drive. Early hard disk drive had removable media, however, a hard disk drive today typically a sealed unit with fixed media. Hard disk drive was introduced in September 13, 1956 as data storage for an IBM accounting computer and it was originally developed for use with general purpose computers. In the 21st century, application for hard disk drive has expanded to include digital video recorders, digital audio players, personal digital assistant, digital camera and video game consoles. Most hard drives are permanently stored in an internal drive bay at the front of the computer and are connected with one ATA / SCSI cable and power cable.

A hard disk drive

Technology of Hard Disk Drive

Hard disk drive record data by magnetizing ferromagnetic material directionally to represent either a 0 or 1 binary digit. It read the data back by detecting the magnetization of the material. A typical hard disk drive design consists of a spindle which holds one or more flat circular disk called platters, onto which the data are recorded. The platters are made from a non-magnetic material. Usually aluminium alloy or glass, and are coated with a think layer of magnetic material. Older disk used iron(III) oxide as the magnetic material, but current disk use a cobalt-based alloy.

The platter are spun at very high speeds. The information to a platter as it rotates past devices called read-and-write heads that operate very close over the magnetic surface. The read-and-write head is used to detect and modify the magnetization of the material immediately under it. For each platter surface on the spindle there is one head.

The older hard disk drive read data on the latter by sensing the rate of change of the magnetism in the head. These head had small coils and it worked much like magnetic-tape playback heads although not in contact with the recording surface. As data density increased, read heads using magneto resistance (MR) came into use. Later development made use of spintronics. In these heads, the magneto resistive effect was much greater that in earlier types, and was dubbed "giant" magneto resistance (GMR).

Hard disk head are kept from contacting the platter surface by the air that is extremely close to the platter. While the record and playback head are mounted on a block called a slider and the surface next to the platter is shaped to keep it just barely out of contact. It is a type of air bearing.

The magnetic surface of each platter is conceptually divided into many small sub-micrometer-sized magnetic regions. Each of which used to encode a single binary unit of information. In modern drives, the small size of the magnetic regions creates the danger that their magnetic state might be lost because of thermal effects. To cover this, the platter are coated with two parallel magnetic layers which separated by a 3-atom-thick layer of the non-magnetic element ruthenium and the two layers are magnetized in opposite orientation.

Architecture of hard disk drive

The stator windings are copper-colored and the motor has an external rotor. The spindle bearing is in the centre while to the left of centre is the actuator with a read-write head under the tip of its very end. The orange stripe along the side of the arm, a thin printed-circuit cable, connects the read-write head to the hub of the actuator. The flexible, that 'U'-shaped, ribbon cable barely visible below and to the left of the actuator arm is the flexible section. One end on the hub that continues the connection from the head to the controller board on the opposite side. The head support arm is very light but also rigid. While, in the modern drive, acceleration at the head reaches 250 gs. The silver-colored structure at the upper left is the top plate of the permanent-magnet and moving coil "motor" that swings the heads to the desired position. Beneath this plate is the moving coil, attached to the actuator hub, and beneath that is a thin neodymium-iron-boron (NIB) high-flux magnet. That magnet is mounted on the bottom plate of the "motor".

The coil is shaped rather like an arrowhead and it is made of doubly-coated copper magnet wire. The inner layer is insulation and the outer is thermoplastic, which bonds the coil together after it's wound on a form and making it self-supporting. Considering that current flows radically outward along one side of the arrowhead and radically inward on the other. The surface of the magnet is half N pole, half S pole and the dividing line is midway and radical.

A hard disk drive with the platters and spindle motor hub

Size of the hard disk drive

The hard disk became colloquially named after the corresponding floppy-disk drives types. The following is the different size of the hard disk drive:

8 inch

The 1st size of the compatible hard disk drive is the Shugart Associates, in 1979

5.25 inch

In 1980, this smaller size of hard disk drive is the 1st used in an hard disk drive and it was the same size as full height 5¼ inch diameter floppy disk drive.

3.5 inch

In 1984, by Rodime, this smaller size was 1st used in a hard disk drive.

2.5 inch

Prairie Tek had introduced this smaller size hard disk drive in 1988 and there is no corresponding floppy disk drive.

1.8 inch

This size of hard disk drive was originally introduced by Integral Peripherals in 1993.

1 inch

In 1999, this size of hard disk was introduced as IBM;s Microdrive.

0.85 inch

In January 2004, Toshiba had announced this type of hard disk drive.

5¼" full height 110 MB HDD

Six hard drives with 8", 5.25", 3.5",2.5",1.8",and 1" disk

Floppy Disk

Floppy Disk is another magnetic storage; it's cased in a square or rectangular plastic shell. This disk only can be read and written by a floppy disk drive (FDD). There are many different types of floppy disks, such as 8 inch, 5¼-inch, and the most common or the smaller is 3½-inch. Into tracks, in tracks got sector and in the sector is the bytes.

The disk is divided into tracks (brown the tracks) and the sector (yellow is the sector).

8 Inch Floppy Disk

The first floppy disk was invented is 8 Inch floppy disk by IBM. The first floppy disk was called the "memory disk" it holding 80 kilobytes and its Single Sided Single Density (SSSD) but this floppy disk can read-only. Memorex 650 was the first read-write floppy disk drive was invented by Memorex in 1972. It had a data capacity of 175kilobytes, with 50 tracks, 8 sector per track, and 448 bytes per sector. In 1973, IBM invented a floppy disk drive, its same with Memorex 650 which it can read-write floppy disk. The different is the capacity; it can store up to 250¼ kilobytes on the same disk. This disk was divided into 77 tracks, with 26 sector per track, and 128bytes per sector. In 1976 IBM introduced 500 kilobytes Double Sided Single Density (DSSD). A year after that IBM introduced the 1 to 1.2 Megabytes disk which is Double Sided Double Density (DSDD).

The 8 Inch floppy disk drive with the floppy disk.

The 8 Inch Floppy disk.

5¼ Inch Floppy Disk

In 1976 the 5¼ Inch Floppy Disk was invented because of the size of the 8 Inch Floppy Disk is so large for the desktop. The first disk only cans storage up to 98.5 Kilobytes, later it was increased to 110 kilobytes. Double-sided drive was introduced in 1978 it doubling the capacity and increased the capacity to 360 kilobytes. At that time floppy drive was the primary storage device. The operating system was usually boot from the floppy disk. In the early of 1980 the quad density was invented, with 96 tracks per inch, it has been increasing the capacity to 720 kilobytes. In 1984 the high density disk appeared. The disk used 96 tracks per inch combined with a higher density magnetic media to provide 1200 kilobytes or 1.2 megabytes.

The 5¼ Inch floppy disk drive.

The 5¼ Inch floppy disk.

3½ Floppy Disk

The 3½ floppy disk is different compare to previous floppy disk it had the rigid case's slide-in-place metal cover, the advantage by adding the rigid case's slide-in-place metal cover is to protect the disk surface from the physical contact. The other different is the shell. The 3½ floppy disk shell is harder compare to the previous floppy disk. The single-sided 3½ inch floppy disk capacity is 360 kilobytes which same with the single-sided 5¼ inch floppy disk. In 1986 Apple introduced the double-sided floppy disk which has the 800 kilobytes capacity, around the same time the 720 kilobytes double-sided double density MFM (Modified Frequency Modulation) disks began to appear on PC-compatibles. In 1987 a newer and better MFM- based was invented which can store 1440 kilobytes or 1.44 megabytes. This floppy disk is high-density and displayed as "HD" on the bottom of the floppy disk. Another floppy disk is extended-density or "ED" which can store 2880 kilobytes or 2.88 megabytes

The 3½ Inch floppy disk drive.

The 3½ Inch floppy disk.

Magnetic stripe card

A magnetic stripe card, sometimes called magstripe, is a type of card capable of storing data by modifying the magnetism of tiny iron-based magnetic particles on a band of magnetic material on the card. It is read by physical contact and swiping past a reading head. They may also contain RFID tag which is a transponder device or a microchip mostly used for business premises access control or electronic payment. Magnetic stripe cards are commonly used in credit cards, identity cards, and also the transportation tickets.

The process of attaching a magnetic to a plastic card was invented by IBM under a contract with the US government for a security system. Forrest Parry, an IBM Engineer, had the idea of securing a piece of magnetic tape, the predominant storage medium at the time, to a plastic card base.

There were a number of steps required to convert the magnetic striped media into an industry acceptable device. These steps included:

Creating the international standards for stripe record content, including which information, in what format and using which defining codes.

Field testing the proposed device and standards for market acceptance.

Developing the manufacturing steps need to mass produce the large number of cards require.

Adding stripe issues and acceptance capabilities to available equipment.

The magnetic stripe is contained in a plastic-like film. The magnetic stripe is located 0.233 inches (5.66mm) from the edge of the card, and is 0.375 inches (9.52mm) wide. The magnetic stripe contains three tracks, each 0.110 inches (2.79mm) wide. Tracks one and three are typically recorded at 210 bits per inch (8.27 bits per mm), while track two typically has a recording density of 75 bits per inch (2.95 bits per mm). Each track can either contain 7-bit alphanumeric characters, or 5-bit numeric characters. Track 1 standards were created by the airlines industry (IATA). Track 2 standards were created by the banking industry (ABA). Track 3 standards were created by the Thrift-Savings industry. Magstripes following these specifications can typically be read by most point-of-sale hardware, which are simply generic general-purpose computers that can be programmed to perform specific tasks. Examples of cards adhering to these standards include ATM cards, bank cards (credit and debit including VISA and MasterCard), gift cards, loyalty cards, driver's licenses, telephone calling cards, membership cards and nearly any application in which value or secure information is not stored on the card itself.

Smart cards are a newer generation of card containing an integrated circuit chip. The card may have metal contacts connecting the card physically to the reader, while contactless cards use a magnetic field or radio frequency (RFID) for proximity reading.

Hybrid smart cards include a magnetic stripe in addition to the chip-this is most commonly found in a payment card, so that the cards are also compatible with payment terminals that do not include a smart card reader.

Magnetoresistive Random Access Memory (MRAM)

Magnetoresistive Random Access Memory (MRAM) is a non-volatile computer memory technology that uses electron spin to store information. MRAM can replace all the memory in our computers. It can resist high radiation, and can operate in extreme temperature conditions.

Description

Unlike other RAM chip technologies, in MRAM data is not stored as electric charge or current flows, but by magnetic storage elements. The elements are formed from 2 ferromagnetic plates. One of the two plates is a permanent magnet set to a particular polarity; the other's field will change to match that of an external field. A memory device is built from a grid of such 'cell'. A particular cell is (typically) selected by powering an associated transistor which switches current from a supply line through the cell to ground. Due to the magnetic tunnel effect, the electrical resistance of the cell changes due to the orientation of the fields in the two plates. Typically if the two plates have the same polarity this is considered to mean "0", while if the two plates are of opposite polarity the resistance will be higher and this means"1".

The toggle mode, uses of a multi-step write with a modified multi-layer cell. The cell is modified to contain an "artificial antiferromagnet" where the magnetic orientation alternates back and forth across the surface, with both the pinned and free layers have only two stable states, which can be toggled from one to the other by timing the write current in the two lines so one is slightly delayed, thereby "rotating" the field. Any voltage less than the full write level increase its resistance to flipping.

Overall

MRAM has similar speeds to SRAM, similar density of DRAM but much lower power than DRAM, and is much faster and suffers no degradation over time compare to flash memory.

Conclusion

There are many types of magnetic storage device. One of them is hard disk drive. Hard disk drive can be internal or external from the computer. In market now, there are a lot of different capacities available. Example, hard disk with the 80 GB, it's the smallest in the market now. While the capacity of hard disk drive up to 1 terabyte which available in market today. It store data permanently which can store until the hard disk drive crash. Beside hard disk drive, there are also got other types of magnetic storage device, its floppy disk. Standard floppy disks with the high-density can store data up to 1.44 MB. But the more the other floppy disk with the extended-density can store data up to 2.88 MB. Although the floppy disk is small and thin but the capacity are smaller compare to other USB flash drive it has become unpopular right now. Another example of magnetic storage device is magnetic stripe card. Magnetic stripe cards are the most common use and see in our daily life as we can commonly found magnetic stripe cards in credit cards, identity cards, and also the transportation tickets. MRAM also is one of the examples of magnetic storage device. MRAM is a non-volatile memory that store information in our computer. It also called as "the ideal memory". One of the advantage of the MRAM is it can resist high radiation, and can operate in extreme temperature conditions.

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