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IELTS Academic Reading 29 sẽ giúp các bạn biết được cách thức làm bài thi cũng như củng cố kiến thức của mình, chuẩn bị tốt cho kì thi sắp tới. Mời các bạn tham khảo. | IELTS Academic Reading 29 You are advised to spend about 20 minutes on Questions 28 - 40. HARD DISK DRIVE TECHNOLOGY A few years ago a query about the health of a person s hard disk drive would have been met with a blank stare. Nowadays almost everyone is aware of this remarkable electronic storage medium that is part of every modern computer even though most users remain ignorant of the complexity of hard drive technology. In the early days of computing an information record of a computer s memory content was kept on punched cards similar to the way in which an automated piano stores the keynote sequences on a piano roll. Later magnetic tape was used to store electronic signals and is still the favoured means of economically backing up the contents of hard drives. However accessing information sequentially stored on tape is slow since the electroniodata must be input through a fixed head in a single pass. Hard disk drives solve this problem by incorporating a spinning platter on which magnetic data can be made accessible via a moving head that reads and writes information across the width of the disk. It is analogous to the way in which a person can choose to play a particular track on a CD player by causing the arm to move the head across the disk. The CD player is in fact necessarily similar in design to a hard drive although there are significant differences in speed of data access. Most modern hard drives incorporate several platters to further reduce the time spent seeking the required information. Also some newer drives have two heads one for reading and a second head for writing data to disk. This separation of tasks enables much higher densities of magnetic information to be written on the platter which increases the capacity of the hard drive. There are three important ways in which the capacity of hard disks has been increased. First the data code itself has been tightened with express coding techniques. Second as previously noted the head technology .
