09 July 2009

Hard disk

The invention: A large-capacity, permanent magnetic storage device built into most personal computers. The people behind the invention: Alan Shugart (1930- ), an engineer who first developed the floppy disk Philip D. Estridge (1938?-1985), the director of IBM’s product development facility Thomas J. Watson, Jr. (1914-1993), the chief executive officer of IBM The Personal Oddity When the International Business Machines (IBM) Corporation introduced its first microcomputer, called simply the IBM PC (for “personal computer”), the occasion was less a dramatic invention than the confirmation of a trend begun some years before. A number of companies had introduced microcomputers before IBM; one of the best known at that time was Apple Corporation’s Apple II, for which software for business and scientific use was quickly developed. Nevertheless, the microcomputer was quite expensive and was often looked upon as an oddity, not as a useful tool. Under the leadership of Thomas J. Watson, Jr., IBM, which had previously focused on giant mainframe computers, decided to develop the PC. A design team headed by Philip D. Estridge was assembled in Boca Raton, Florida, and it quickly developed its first, pacesetting product. It is an irony of history that IBM anticipated selling only one hundred thousand or so of these machines, mostly to scientists and technically inclined hobbyists. Instead, IBM’s product sold exceedingly well, and its design parameters, as well as its operating system, became standards. The earliest microcomputers used a cassette recorder as a means of mass storage; a floppy disk drive capable of storing approximately 160 kilobytes of data was initially offered only as an option. While home hobbyists were accustomed to using a cassette recorder for storage purposes, such a system was far too slow and awkward for use in business and science. As a result, virtually every IBM PC sold was equipped with at least one 5.25-inch floppy disk drive. Memory Requirements All computers require memory of two sorts in order to carry out their tasks. One type of memory is main memory, or random access memory (RAM), which is used by the computer’s central processor to store data it is using while operating. The type of memory used for this function is built typically of silicon-based integrated circuits that have the advantage of speed (to allow the processor to fetch or store the data quickly), but the disadvantage of possibly losing or “forgetting” data when the electric current is turned off. Further, such memory generally is relatively expensive. To reduce costs, another type of memory—long-term storage memory, known also as “mass storage”—was developed. Mass storage devices include magnetic media (tape or disk drives) and optical media (such as the compact disc, read-only memory, or CDROM). While the speed with which data may be retrieved from or stored in such devices is rather slow compared to the central processor’s speed, a disk drive—the most common form of mass storage used in PCs—can store relatively large amounts of data quite inexpensively. Early floppy disk drives (so called because the magnetically treated material on which data are recorded is made of a very flexible plastic) held 160 kilobytes of data using only one side of the magnetically coated disk (about eighty pages of normal, doublespaced, typewritten information). Later developments increased storage capacities to 360 kilobytes by using both sides of the disk and later, with increasing technological ability, 1.44 megabytes (millions of bytes). In contrast, mainframe computers, which are typically connected to large and expensive tape drive storage systems, could store gigabytes (millions of megabytes) of information. While such capacities seem large, the needs of business and scientific users soon outstripped available space. Since even the mailing list of a small business or a scientist’s mathematical model of a chemical reaction easily could require greater storage potential than early PCs allowed, the need arose for a mass storage device that could accommodate very large files of data. The answer was the hard disk drive, also known as a “fixed disk drive,” reflecting the fact that the disk itself is not only rigid but also permanently installed inside the machine. In 1955, IBM had envisioned the notion of a fixed, hard magnetic disk as a means of storing computer data, and, under the direction of Alan Shugart in the 1960’s, the floppy disk was developed as well. As the engineers of IBM’s facility in Boca Raton refined the idea of the original PC to design the new IBM PC XT, it became clear that chief among the needs of users was the availability of large-capability storage devices. The decision was made to add a 10-megabyte hard disk drive to the PC. On March 8, 1983, less than two years after the introduction of its first PC, IBM introduced the PC XT. Like the original, it was an evolutionary design, not a revolutionary one. The inclusion of a hard disk drive, however, signaled that mass storage devices in personal computers had arrived. Consequences Above all else, any computer provides a means for storing, ordering, analyzing, and presenting information. If the personal computer is to become the information appliance some have suggested it will be, the ability to manipulate very large amounts of data will be of paramount concern. Hard disk technology was greeted enthusiastically in the marketplace, and the demand for hard drives has seen their numbers increase as their quality increases and their prices drop. It is easy to understand one reason for such eager acceptance: convenience. Floppy-bound computer users find themselves frequently changing (or “swapping”) their disks in order to allow programs to find the data they need. Moreover, there is a limit to how much data a single floppy disk can hold. The advantage of a hard drive is that it allows users to keep seemingly unlimited amounts of data and programs stored in their machines and readily available. Also, hard disk drives are capable of finding files and transferring their contents to the processor much more quickly than a floppy drive. A user may thus create exceedingly large files, keep them on hand at all times, and manipulate data more quickly than with a floppy. Finally, while a hard drive is a slow substitute for main memory, it allows users to enjoy the benefits of larger memories at significantly lower cost. The introduction of the PC XT with its 10-megabyte hard drive was a milestone in the development of the PC. Over the next two decades, the size of computer hard drives increased dramatically. By 2001, few personal computers were sold with hard drives with less than three gigabytes of storage capacity, and hard drives with more than thirty gigabytes were becoming the standard. Indeed, for less money than a PC XT cost in the mid-1980’s, one could buy a fully equipped computer with a hard drive holding sixty gigabytes—a storage capacity equivalent to six thousand 10-megabyte hard drives.


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