С! 44 . storage devices 1) storage media are classified as primary storage or secondary storage on the basis of combinations of cost, capacity, and access time. the cost of storage devices is expressed as the cost per bit of data stored. the time required for the computer to locate and transfer data to and from a storage medium is called the access time for that medium. capacities range from a few hundred bytes of primary storage for very small computers to many billions of bytes of archival storage for very large computer systems. 2) primary storage has the least capacity and is the most expensive; however, it has the fastest access time. the principal primary storage circuit elements are solid-state devices: magnetic cores and semiconductors. for many years magnetic cores were the principal elements used in digital computers for primary storage. the two principal types of semiconductors used for memory are bipolar and metal-oxide semiconductors (mos). the former is faster, the latter is more commonly used at present. because data can be accessed randomly, semiconductor memories are referred to as random-access memory, or ram. 3) there is a wide range of secondary storage devices. typical hardware devices are rotating electromechanical devices. magnetic tapes, disks, and drums are the secondary storage hardware most often used in computer systems for sequential processing. magnetic tape, which was invented by the germans during world war ii for sound recording, is the oldest secondary storage medium in common use. data are recorded in the form of small magnetized “dots” that can be arranged to represent coded patterns of bits. 4) tape devices range from large-capacity, high-data-rate units used with large data processing systems to cassettes and cartridges used with small systems. magnetic disk storage, introduced in the early 1960s, has replaced magnetic tape as the main method of secondary storage. as contrasted with magnetic tapes, magnetic disks can perform both sequential and random processing. they are classified as moving-head, fixed-head, or combination moving-head and fixed-head devices. magnetic disks are the predominant secondary storage media. they include flexible, or floppy disks, called diskettes. the “floppies” were introduced by ibm in 1972 and are still a popular storage medium to meet the demands of the microcomputer market. 2. ответьте на следующие вопросы, используя информацию из текста: 1. how are storage media classified? 2. what is the access time for storage media? 3. what are the two main types of storage devices? 4. what is the oldest secondary medium and when was it invented? 5. what is a floppy?

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