Types Of Magnetic Storage Devices Computer Science Essay

Types Of Magnetic Storage Devices Computer Science Essay Magnetic storage devices are used to store data in magnetic medium. In this term paper we will discuss about its types and working principle. The main logic is that the data will secure in these storage devices and data will store quickly in these devices. In this term paper we will also discuss the future of these devices. MAGNETIC STORAGE DEVICES Magnetic storage and magnetic recording are terms from engineering referring to 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. As of 2009, magnetic storage media primarily hard disks are widely used to store computer data as well as audio and video signals. HISTORY Before there was magnetic storage for computers, the primary storage medium was punch cards (paper cards with holes punched in to indicate character or binary data) originally invented in the 1890. Although long obsolete in computer use punch cards in various forms are still used in older voting equipment. PUNCH CARD The history of magnetic storage dates back to June 1949 when a group of IBM engineers and scientists began working on a new storage device. What they were working on was the first magnetic storage device for computers, and it revolutionized the industry. On May 21, 1952 IBM announced the IBM 726 Tape Unit with the IBM701 Defense Calculator, marking the transition from punched-card calculators to electronic computers. Four years later, on September 13, 1956 a small team of IBM engineers in San Jose, California, introduced the first computer disk storage system as part of the 305 RAMAC (Random Access Method of Accounting and Control) computers. IBM 305 RAMAC The 305 RAMAC drive could store only 5MB of data on 50 disks each a whopping 24 in diameter. Unlike tape drives RAMACs recording heads could go directly to any location on a disk surface without reading all the information in between. This random accessibility had a profound effect on computer performance at the time enabling data to be stored and retrieved significantly faster than if it were on tape. From these beginnings, the magnetic storage industry has progressed such that today you can store 500GB or more on tiny 3 1/2 drives that fit into a single computer drive bay. IBMs contributions to the history and development of magnetic storage are incredible. Not only did IBM invent computer magnetic tape storage as well as the hard disk drive but it also invented the floppy drive. The first floppy drive was created in 1971. EXAMPLES OF MAGNETIC STORAGE DEVICES HARD DRIVE FLOPPY DRIVE Mini DV TAPE DATA TAPE BACKUP STRIPE ON THE BACK OF DEBIT.CREDIT CARD MAGNETIC RECORDING Magnetic recording is the method of writing data on disk. ANALOG RECORDING 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. DIGITAL RECORDING Instead of creating a magnetization distribution in analog recording, digital recording only need two stable magnetic states, which are the +Ms and -Ms on the hysteresis loop. Examples of digital recording are floppy disks and HDDs. Digital recording is the main process nowadays and probably in the coming future. HARD DISK DRIVE A hard disk drive is a non-volatile storage device that stores digitally encoded data on rapidly rotating rigid (i.e. hard) platters with magnetic surfaces. WORKING A hard disk uses rigid rotating platters. Each platter has a planar magnetic surface on which digital data may be stored. Information is written to the disk by transmitting an electromagnetic flux through a read-write head that is very close to a magnetic material, which in turn changes its polarization due to the flux. A typical hard disk drive design consists of a central axis or spindle upon which the platters spin at a constant rotational velocity. The associated electronics control the movement of the read-write armature and the rotation of the disk and perform reads and writes on demand from the disk controller. The sealed enclosure protects the drive internals from dust, condensation, and other sources of contamination. Contrary to popular belief, a hard disk drive does not contain a vacuum. Instead, the system relies on air pressure inside the drive to support the heads at their proper flying height while the disk is in motion. FLOPPY DRIVE A floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square/rectangular plastic shell. WORKING The following is an overview of how a floppy disk drive writes data to a floppy disk. Reading data is very similar. The computer program passes an instruction to the computer hardware to write a data file on a floppy disk, which is very similar to a single platter in a hard disk drive except that it is spinning much slower, with far less capacity and slower access time. The computer hardware and the floppy-disk-drive controller start the motor in the diskette drive to spin the floppy disk. The disk has many concentric tracks on each side. Each track is divided into smaller segments called sectors, like slices of a pie. A second motor, called a stepper motor, rotates a worm-gear shaft (a miniature version of the worm gear in a bench-top vise) in minute increments that match the spacing between tracks. The time it takes to get to the correct track is called access time. This stepping action (partial revolutions) of the stepper motor moves the read/write heads like the jaws of a bench-top vise. The floppy-disk-drive electronics know how many steps the motor has to turn to move the read/write heads to the correct track. The read/write heads stop at the track. The read head checks the prewritten address on the formatted diskette to be sure it is using the correct side of the diskette and is at the proper track. This operation is very similar to the way a record player automatically goes to a certain groove on a vinyl record. Before the data from the program is written to the diskette, an erase coil (on the same read/write head assembly) is energized to clear a wide, clean slate sector prior to writing the sector data with the write head. The erased sector is wider than the written sector this way, no signals from sectors in adjacent tracks will interfere with the sector in the track being written. The energized write head puts data on the diskette by magnetizing minute, iron, bar-magnet particles embedded in the diskette surface, very similar to the technology used in the mag stripe on the back of a credit card.The magnetized particles have their north and south poles oriented in such a way that their pattern may be detected and read on a subsequent read operation. The diskette stops spinning. The floppy disk drive waits for the next command. FUTURE Magnetoresestive Random Access Memory A new type of magnetic storage, called Magnetoresistive Random Access Memory or MRAM, is being produced that stores data in magnetic bits based on the TMR (Tunnel Magneto resistance) effect. Its advantage is non-volatility, low power usage, and good shock robustness. WORKING Unlike conventional 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 two ferromagnetic plates, each of which can hold a magnetic field separated by a thin insulating layer. One of the two plates is a permanent magnet set to a particular polarity the others field can be changed to match that of an external field to store memory. This configuration is known as a spin valve and is the simplest structure for a MRAM bit. A memory device is built from a grid of such cells. The simplest method of reading is accomplished by measuring the electrical resistance of the 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. By measuring the resulting current, the resistance inside any particular cell can be determined, and from this the polarity of the writable plate. Typically if the two plates have the same polarity this is considered to mean 1, while if the two plates are of opposite polarity the resistance will be higher and this means 0.

Running Head: Airline Industry

Globalisation of world economies is forcing countries and companies alike to improve their competitiveness in the global market. This being the case, the American airlines industry is set for a shake-up given that thee sector is heavily shielded from external competition by the American government (Marketplace, 2008).This is because the ever increasing demand for national and international travel is creating bigger markets for airlines that can efficiently meet travellers needs, something that American companies become disadvantaged. In order to position themselves better in the global market, global airlines have been merging in order to take advantage of economies of scale and increase connectivity among their routes (Haran, 2008).The biggest merger so far has been between the Holland based KLM and the Paris   based Air France. With regard to American airline companies, the government has protected the industry for too long such that they are loosing out on the good fortunes that have befallen the industry. As a contribution to the debate of current trend in the Unites States' airline industry, this paper shall concentrate on the recent merger indications between several US based airlines that were sparked by Delta and Northwest Airlines.The first section shall deal with the current situation in the industry, the second with the increasing need to open the industry to internal and global competition, and the third section, with reasons behind the current merger trend between within US Aniline companies. The sections shall be followed by a conclusion listing all the microeconomic issues discussed in the paper.Current State of the IndustryThe US airline industry has for long been an oligopolistic market dominated by several airlines. However, the increasing entry of budget airline in the industry has given the bigger players a run for their money, meaning that oligopolistic traits are increasingly being replaced by the competitive characteristics.The bigger a nd old players in the market face the headache of dealing with ageing aircraft that need constant repair (George, 2008). This means that costs of production has been increasing with rime, as the planes get older. Secondly, these big players find themselves being captive of labor unions representing employees, some of whom have operated with the airlines for decades. These kinds of increases in the cost of their operating mean that consumers of their services would pay more for travel.Contrary, budget airlines find themselves with newer aircraft that do not require constant repairs, reason being that they are relatively new in the market. In this regard, the budget airlines are able to operate at lower costs and therefore charge competitive fares for their services, much to the detriment of bigger and well established players.Budget airlines are less affected by union demands. In addition, the older airlines have for many years invested in other facilities whose maintainable increase s the cost of operating their businesses, which further means that budget airlines would continue   to out-compete their well established rivals.

Mystery Stories Sesay Essay

Choose three of the short mystery stories we have studied. In the three you have chosen write about how successful the authors have been in describing the creation of atmosphere, memorable characters and vivid settings. We have been studying four mystery stories, written before 1900. ‘The Beryl Coronet’ ‘The Adventure of the Engineers Thumb’ ‘The Speckled Band’ All written by Sir Arthur Conan Doyle. ‘The Monkeys Paw’ written by W. W. Jacob’s. Three of the stories feature Sherlock Holmes, the famous Victorian detective solving the case. I have chosen to write about ‘The Monkeys Paw’ ‘The Speckled Band’ and ‘The Adventure of the Engineers Thumb’. All three stories feature memorable uses of atmosphere, characters and setting. The characters play an important part in the mystery stories of setting the mood. In ‘The Speckled Band’ and ‘The Adventure of the Engineers Thumb’ the villain’s and victims are very obvious. In ‘The Speckled Band’ the villain is Dr Grimesby Roylott who is step father to Helen Stoner and her late twin sister Julia Stoner. When Helen Stoner first went to meet Sherlock Holmes she told Holmes about her stepfather Dr Gimesby Roylott. Since the death of the twins mum Dr Grimesby Roylott had changed from an outgoing man who like to exchange visits with neighbours into a man that locked him self in his house and only came out to argue with people. Dr Grimesby Roylott was a violent and angry man ‘He is a man of immense strength, and absolutely uncontrollable in his anger’ Holmes can see this by the marks on Helen Stoners wrist where Dr Grimsby Roylott had grabbed hold of her wrist very tightly. When he was practising in India he killed a man ‘In a fit of anger, however, cause by some robberies which had been perpetrated in the house, he beat his native butler to death, and narrowly escaped a capital sentence’ Dr Grimsby Roylott is capable of killing someone and he would do it again if there was a good enough reason, a reason maybe like inheritance. Helen Stoner believes that Dr Grimesby Roylott has been come an angrier man because of all the time he spent in India. Violence of temper approaching to mania has been hereditary in the men of the family, and in my stepfather’s case it had, I believe, been intensified by his long residence in the tropics’. Helen Stoner is the daughter of Dr Grimesby Roylotts late wife. Helen is a very timid woman who is about to be married. She is very scared of her stepfather because of his anger. Helen is always bailing out Dr Grimesby Roylott when he has money problems. Helen was extremely close to her late twin sister, Julia Stoner. Julia was murdered by her stepfather, Dr Grimsbey Roylott â€Å"she died just two years ago, and it is her death that I wish to speak to you about† Helen was not sure what caused Julia’s death. Helen and her sister Julia didn’t like living with their stepfather, they could not live a normal life he was a very evil man â€Å"you can imagine from what I say that my poor sister Julia and I had no great pleasure I our lives† because of their stepfather and his temper. A very memorable character in two of the stories, â€Å"The Speckled Band† and â€Å"The Adventure of the Engineer’s Thumb† is Sherlock Holmes. He is memorable in â€Å"The Speckled Band† because he’s not afraid or intimidated by anything. When Dr Grimesby Roylott went to 221B Baker Street to tell Sherlock Holmes to back off and leave his stepdaughter alone, he bent the poker and threw it in to the fire and said â€Å"I am a dangerous man to fall foul of! † and Sherlock also knew Dr Grimesby Roylott had killed before and was capable of doing it again Sherlock just laughed and said â€Å"He seems like a very amiable person†. He didn’t feel threatened of worried about Dr Grimesby Roylott. Sherlock is also a extremely clever man he could tell when Helen got to his rooms how she travelled just by a few spatters of mud on her coat. â€Å"There is no mystery, my dear madam,’ ‘the left arm of your jacket is spattered with mud in no less than seven places’†. He also managed to solve the mystery of Julia’s death and the whistling Helen had been hearing with minimum clues. Sherlock Holmes is a memorable character in â€Å"The Adventure of the Engineer’s Thumb†, but he isn’t as memorable is this story as he is in â€Å"The Speckled Band† because in â€Å"The Speckled Band† he works out all the clues and solves the mystery but in â€Å"The Adventure of the Engineer’s Thumb† He is given all the clues he just has to put them all together to get the conclusion. In ‘The Adventure of the Engineers Thumb’ the villain is Colonel Lysander Stark. He is very thin and pale man of middle size. Although he was very thin he was bright eyed and had a brisk step. Colonel Lysander Stark is a sneaky, evil German man. â€Å"Mr Hatherly? † said he, with something of a German accent†. Lysander Stark has killed before â€Å"Fritz! Fritz! She cried in English remember your promise after the last time. You said it should not be again†. Elsie and Lysander Stark know each other very well so Elsie knows his real name, Fritz. Victor Hatherly is the victim he is very weary of Colonel Lysander Stark because when they first met Lysander Stark ask a very weird question â€Å"I have it from the same source that you are both an orphan and a bachelor, and are residing alone in London†. Lysander Stark asked this because then he knew for certain that if anything happened to him no one would know he was missing or even in fact dead. After Lysander Stark had asked this question Victor became increasingly careful of what he said around and to Lysander Stark. Victor Hatherly ignores Elise when she tells him â€Å"I would go. I should not stay here. There is no good for you to do†. Victor ignores Elsie because he needs the money that Lysander Stark is paying him. Victor’s brain is telling him that he shouldn’t be there and that he should go but chooses not to listen to his brain because he wanted the money. But I am of a headstrong nature, and the more ready to engage in an affair when there is some obstacle in my way†. Elise is a very young and weary woman. She is constantly bossed about by Lysander Stark. She is fully aware of what he is capable of and knows what’s going on. She tells Victor to go and get far away from the house because she knows something bad is going to happen. But he doesn’t listen to her so she has to take care of him ‘â€Å"Come! Come! ’ she cried breathlessly. ‘They will be here in a moment. They will see your not there. Oh, do not waste the precious time, but come†Ã¢â‚¬â„¢. She is trying to hide victor because she cares for him and doesn’t want to see him be hurt. In â€Å"The Monkeys Paw† there is no obvious villain but you could say that Sergeant Major Morris is the protagonist because he is the one that introduces ‘The Monkeys Paw’ and delivers various warnings that the Whites do not head. â€Å"If you keep it, don’t blame me for what happens. Pitch it on the fire again, like a sensible man† he’s all most guaranteeing that something bad is going to happen because he says that when it does don’t blame him. So he knows ‘The Monkeys Paw’ is not a good thing Mrs White is the one that wants to keep â€Å"The Monkeys Paw† and keep the wishes â€Å"I want it,’ she said quietly. ‘You’ve not destroyed it? ’† She wanted ‘The Monkeys Paw’ so she could get her son back . She thought that if the first wish was granted that the second one would be to â€Å"we had the first wish granted,’ said the old woman, feverishly; ‘why not the second? ’†. She wanted the second wish granted because she wanted to bring her son back from the dead. Mr White just wanted to get rid of â€Å"The Monkeys Paw† because he knew it would only cause trouble and more harm than good â€Å" Good God, are you mad! he exclaimed when Mrs White asked where ‘The Monkeys Paw’ was. He just wanted to get rid of it. Herbert is very sceptical about ‘The Monkeys Paw’ he doesn’t believe that the wishes are true â€Å"how could wishes be granted in these days? And if they could two hundred pounds hurt you, father† he’s saying that wishing for the two hundred pounds could mean that Mr White might have to sacrifice something important to him, which is exactly what happens when Herbert dies and they get the compensation.

How Does Shakespeare Present the Characters Macbeth and...

How does Shakespeare present the characters of Macbeth and Lady Macbeth in Act 1? Macbeth is a dramatic play which tells the story of the downfall of a ‘Nobleman’ who becomes a ‘tyrant’. In Act one Shakespeare introduces the characters Macbeth and Lady Macbeth using a range of dramatic devices. At the start of the play Macbeth is introduced from two different perspectives. He is firstly introduced by the three witches whom are discussing a meeting with him ‘There to meet with Macbeth’. This scene would create immense tension for the audience as the presence of the witches in the play would indicate a series of evil and sinister events occurring later on in the play. King James I was also afraid of witches so this scene would tense the†¦show more content†¦Macbeth then asks Banquo that if his prophecies are coming true that ‘Do you not hope your children shall be kings,’ and Banquo replies ‘And oftentimes, to win us to our harm, The instruments of darkness tell us truths;’ This shows the audience that Banquo believes that the witches are telling them simple truths to deceive them and influence them to the path of evil. It also gives the audience the impression that Macbeth is hungry for power and fortune and is willing to take evil routes. In this part of the scene Shakespeare uses stage craft to create suspense. Macbeth moves ‘Aside’ when he refers to the witches so the audience can hear his thoughts. Act 1 Scene 4 King Duncan receives Macbeth and Banquo with appreciation for their achievements towards the success if the battle. King Duncan announces that his eldest son Malcolm would inherit the throne from him and be called King of Scotland after him ‘Our eldest, Malcolm, whom we name hereafter The Prince of Cumberland’. This would leave the audience and Macbeth in confusion as the witches Prophesized that Macbeth would become king and King Duncan had just stated that his son will inherit the throne after him. It would also leave them questioning how Macbeth will claim this title as it is his desire to become king. At this point Macbeth would become even more ambitious to become king as he has been toldShow MoreRelatedOverview of Macbeth1746 Words   |  7 PagesNot surprisingly, Macbeth has received volumes of critical commentary over the years. Not only is the play an audience favorite, but its complex characterization, deeply woven themes, and characteristic Shakespearean style make it rich ground for scholarly inquiry. 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This quote is very significant, as it is an elaborate theme throughout the play. Also, the word fair means good, and foul means evil. Fair is foul and foul is fair is a theme that demonstrates how appearances often differs from reality. ThisRead MoreShakespeares Macbeth, Why We Still Study This Play in Present Day?1108 Words   |  5 PagesGeorgia O’Neill Year 11 essay: Macbeth WHY DO WE STILL STUDY THIS PLAY IN 2012? The legendary tale of Macbeth has endured the test of time and is still a largely studied and watched play in 2011. There are numerous reasons why this is, not only does this classic play have a fascinating story and characters, it also has countless themes that still present valuable lessons to be learnt in this day and age. One of those important lessons shown in this dramatic play includes the deceptive nature