Степени сравнения прилагательных.
Для английского языка характерны два способа образования степеней сравнения прилагательных. Односложные прилагательные и двусложные с ударением на первом слоге образуют сравнительную степень с помощью суффикса er, а превосходную степень с помощью суффикса est.
Этот куб небольшой, а тот меньше. This cube is small but that cube is smaller.
После сравнительной степени употребляется союз than.
Отрезок АВ длиннее, нем отрезок CD. Segment. АВ is longer than segment CD.
Многосложные прилагательные образуют сравнительную степень при помощи слова more, а превосходную – при помощи the most.
difficult – more difficult – the most difficult
Степени сравнения некоторых прилагательных и наречий образуются от разных основ.
many (much) more the most
little less the least
good (well) better the best
bad worse the worst
far farther /further the farthest/furthest
Far (далекий, далеко) имеет две формы степеней сравнения. Форма farther, the farthest употребляется в прямом смысле (при обозначении расстояния), а форма further, the furthest – в переносном смысле (в значении “дальнейший”).
This is the farthest region. Это самый удаленный район.
Further discussion is not needed. Дальнейшая дискуссия не требуется.
II. Употребите наречия и прилагательные, данные в скобках, в сравнительной или превосходной степени.
You have got (much) time than I have.
Your collection of records is (good) than mine.
My recorder is (bad) than yours.
Perhaps my recorder is the (bad) of all.
You have a (good) opportunity to do it.
This is the (much) important thing for me.
I think it is (little) important for him than for me.
The town is (far) than you think.
III. Дайте русские эквиваленты, следующим сочетаниям
integrated circuit manufacturer, RAM chips, word size, production technique, minicomputer memory, automatic tape library system, mass storage system, head-per-track discs, video-recorded mag tape memory, disc pack drive, circuit component requirement, bubble chip, performance factor, data module.
1. Прочитайте текст и перечислите преимущества каждого из типов памяти.
We can consider that there are four categories of memory. Moving out from the heart of the system, they are:
Internal memory
MOS random access memories
Bipolar random access memories
Gap-filler memory
Charge-coupled devices
Magnetic bubble devices
Electron beam accessed memories
Head-per-track discs
Secondary memory
'Winchester' discs
Magnetic tape units
Mass storage systems
Automatic tape library systems
Video-recorded mag tape memory
Intel introduced the first IK RAM memory back in 1971. This was followed in 1973 by the 4K RAM chip. Now the 4K chip is available from nearly every major integrated circuit (IС) manufacturer in the business.
RAM's are orginized in matrixes of words by bits. For instance, 4K RAM's are offered cither as 4K words by one bit or IK by 4 bits. The total number of bits is the same, but the parts are not interchangeable. All of the available 16K RAM chips have been organized as 16K by 1, however, so that computer manufacturers can stack chips in parallel groups depending on their word sizes.
There are two basic types of RAM's, static and dynamic. The differences are significant. Dynamic RAM's are those which require their contents to be refreshed periodically. They require supplementary circuits to provide the refreshing and to assure that conflicts don't occur between the refreshing and the normal read/write operations. Even with those extra circuits, however, dynamic RAM's require fewer on-chip components per bit than do static RAM's which don't require refreshing.
The fact that they require fewer components makes it possible to achieve higher densities with dynamic RAM's than are possible with static RAM's. And the higher densities lead to lower costs per bit. The production techniques for the two kinds of chips are identical. Therefore, the cost per unit quickly becomes the cost for mass producing one chip. Since the chips cost about the same amount to build whether they store 4K or 16K, higher densities lead to lower costs per bit.
Static RAM's are easier to design with, however, and compete well in applications where less memory is to be provided since their higher cost then becomes less important. They are often chosen for minicomputer memory, especially for micros.
Because they require more components per chip, making high bit densities more difficult to achieve, the introduction of static RAM's of any given density follows that of dynamic versions.
There is another trade-off to be made with semiconductor random access memories too, in addition to the choice between static and dynamic types. The trade-off is between MOS and bipolar circuitry. Bipolar devices are faster, but have not yet achieved densities (and hence the lower costs) of MOS.
Charge-coupled devices
Charge-coupled devices have been around for a while – both Intel and Fairchild have been delivering 16 Kbit versions since 1975 – but their sales
volumes have been minimal.
CCD's, because of their lower circuit component requirements, can potentially achieve higher densities than can the RAM's with which they usually compete. Because the higher densities are easier to achieve, CCD's of any given capacity have preceded RAM's in the marketplace. RAM's, in fact, are fabricated with the same silicon processing technology; and can borrow the techniques developed for CCD's preceding them. But RAM's do catch up.
When 16K RAM's were announced, interest in the 16K CCD's sank. Then in 1977, 64K CCD's were introduced and made available in sample quantities. So they are ahead for a while.
CCD's sometimes lose to RAM's on the basis of speed. Charge-coupled devices are inherently slower because their internal structure consists of serial delay lines (shift registers). Data circulates continuously through the devices.
One of the key performance factors to understand about CCD's is that they are a combination of random access and serial access devices. It is possible to randomly access a block of data on a CCD, but then the block must be read out serially.
The shift-register nature of the devices causes manufacturers to orginize them in complicated ways in attempt to compensate for their slower access times. On the other hand, they do have fast shift rates and can transfer data serially at speeds around 5M bps. By paralleling the chips to construct wider paths, it is possible to move 2kb blocks of data in as little as 500 μsec. This is a respectable rate at which to feed a cpu. Some CCD systems are significantly faster. Fairchild offers a 8mb memory.
Magnetic bubble devices
Bubble memory devices actually have become available only in the last ten years. Bubbles are different from semiconductor memories in that they are magnetic devices, where the absence or presence of a magnetic domain is the basis for a binary one or zero. A magnetic 'bubble' is in reality a cylindrical magnetic domain with a polarization opposite that of the magnetic film in which it is contained. These cylinders appear under a microscope as small circles – hence the name – with diameters measuring 2 to 20 microns. The size of a bubble is determined by the material characteristics and by the thickness of the magnetic film.
Bubbles are moved or circulated by establishing a magnetic field through a separate conductor mounted adjacent to the bubble chip. Still, a large
portion of the bubble chip itself also must be given over to circuitry for generating, detecting, and annihilating the bubbles.
The bubble memory is used for local storage; the memory adds only a few pounds to the weight of the terminal. Like CCD's the bubble devices continually recirculate their contents, but they are more useful than CCD's since they don't lose their contents when the power is off'.
Bubble memories are particularly well-suited to such applications because of their physical advantages (low power requirements and light weight) and speed advantages over electromechanical devices such as cassettes and floppies.
BMD's can operate in an endless serial loop fashion or in an organization with bit-serial minor loops feeding major loop registers, in this respect they are similar to CCD's. Current typical data shift rates are 100 Kbps to 300Kbps; and by paralleling or multiplexing, eight chips can transfer 1kb in less than 10 μsec.
Secondary Memory
'Winchester' discs
Many improvements in disc memories have been made in the 1970s. This brief treatment allows us to update only the major trends, obviously not all the new developments. And of the major trends, two are most significant: the 'Winchester' developments of the data module (where the read/write heads are made integral to the disc pack), and of the large fixed disc pack drives with capacities of 300Mb or more. Functionally, discs have always had the advantage of immediate playback, immediate reuse, and long-term storage. An equally important quality is reliabiliy. IBM's 'data module" with integral heads, media, and spindle was a big step. Memorex sells a similar unit called the Data Mark Module which differes from IBM's in having the rotation mechanism and actuator coil in the pack as well.
IV. Опираясь на свои знания и опыт, дополните схему-классификацию памяти и расскажите о памяти, опираясь на схему и информацию, почерпнутую из текста.
Fig. 5. Memory classification.
2. Types of data processing
Batch processing
An early type of processing was called batch processing. In this type of processing, the user is off-line to the computer. The users have to give their jobs to the computer operator. The operator decides the order of the jobs. That is, the operator schedules the jobs. This type of processing has several disadvantages:
The user is off-line to the computer and cannot control his own job.
The user has to go to the computer operator's office to give him new data and new program.
If there is a mistake in the data, the user does not know until all the jobs are finished.
The computer does not start the second job until the first one is finished. This means that the total processing time is longer than necessary.
Remote batch processing
Some of the problems of batch processing can be solved by using more peripherals. Users can have their own card reader and printer linked to the
CPU. A central operator still schedules the jobs. This arrangement is known as remote batch processing.
In remote batch processing, the user does not have to go to the computer operator's office. This is an advantage. However, the user cannot start or stop jobs. The operator is still responsible for scheduling jobs.
Multiprocessing
The earliest operating systems allowed only one job to be run at a time. The CPU is not executing instructions all the time.
The processor in the CPU executes instructions very fast. It can execute up to a million instructions per second. But at certain moments, e.g. waiting for data, the CPU is not active. That is, the CPU is not executing any more instructions. A CPU is inactive during a read-from-disc, and again during a write-to-disc. If there are many input or output operations, the CPU activity can become very small.
Multiprogramming allows several jobs to be run at the same time. Now the CPU is active all the time.
At any moment, the CPU is executing instructions from only one program. However, more than one program is running. Multiprogramming of this kind is provided 6y more advanced operating system.