Computer Science. The English Language Perspective - Беликова (1176925), страница 8
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Today’s generic “floppy” disks are3-1/2” in diameter, encased in a hard plastic cover, and capableof storing 1.44MB of data.Hard disks, the disks on the hard drive that comes with thecomputer, consist of several disks (platters) attached to aspindle that rotates. Each platter has its own read/write head.Hard drives rotate at a much higher speed than floppy drives,and the read/write heads do not actually touch the surface ofthe platters but, rather, float above them.45Compact DisksThe world of compact disks and their drivers looks likeacronym soup: CD-DA, CD-ROM, CD-RW, CD-WORM, DVD.A CD drive uses a laser to read information stored optically ona plastic disk.
Rather than having concentric tracks, there is onetrack that spirals from the inside out. Like other disks, the trackis broken into sectors. Unlike magnetic disks where the tracksnear the center are more densely packed, a CD has the dataevenly packed over the whole disk, thus more information isstored in the track on the outer edges and read in a singlerevolution. In order to make the transfer rate consistentthroughout the disk, the rotation speed varies depending on theposition of the laser beam.The other letters attached to CD refer to various properties ofthe disk, such as formatting, and whether or not theinformation on them can be changed.
CD-DA (Compact DiskDigital Audio) is the format used in audio recordings. Certainfields in the format are used for timing information.CD-ROM (Read-Only Memory) is the same as CD-DA but thedisk is formatted differently. Data is stored in the sectorsreserved for timing information in CD-DA. Read-only memorymeans that the data is permanent on the disk and cannot bechanged.The acronym CD-WORM stands for Write Once, Read Many.This format, which is also called CD-R (Recordable), is usedtypically for archiving data, where the data is not to be changedafter being recorded.CD-RW (Rewritable) allows you to erase disks and reuse them.DVD, which stands for Digital Versatile Disk, can store multimedia presentations that combine audio and video. DVDs alsocome in several formats: DVD-ROM, DVD-R, DVD-RW.Flash MemoryFlash memory is a type of non-volatile memory that can beelectronically erased and reprogrammed. Its name was46invented by Toshiba to express how much faster it could beerased- ‘in a flash’, which means ‘very quickly’.Unlike RAM, which is volatile, flash memory retains theinformation stored in the chip when the power is turned off.This makes it ideal for use in digital cameras, laptops, networkswitches, video game cards, mobile phones and portablemultimedia players.
In addition, it offers fast read access times(although not as fast as RAM), with transfer rates of 12MB persecond. Unlike ROM chips, flash memory chips are rewritable,so you can update programs via software.Flash memory is used in several ways:- Many PCs have their BIOS (basic input/output system)stored on a flash memory chip, so it can be updated ifnecessary.- Modems use flash memory because it allows themanufacturer to support new protocols.- USB flash drives are used to save and move MP3s and otherdata files between computers.New U3 smart drives allow users to store both applications anddata.
They have two drive partitions and can carry applicationsthat run on the host computer without requiring installation.Flash memory cards are used to store images on cameras, toback up data on PDAs, to transfer games in video consoles, torecord voice and music on MP3 players or to store movies onMP4 players. Their capacity can range from 8 MB to severalgigabytes.
The only limitation is that flash cards are often notinterchangeable.Non-von Neumann ArchitecturesThe linear fetch-execute cycle of the von Neumann architecturestill dominates the technology today. However, since 1990,alternative parallel-processing systems have entered themarketplace. They have the potential to process much moredata at much higher speeds.One approach to parallelism is to have multiple processorsapply the same program to multiple data sets.
In this approach,47processors often execute the same instructions at the same time,i.e., a common program is run at each processor. This approachis called synchronous processing and is effective when the sameprocess needs to be applied to many data sets. This approach issimilar to that of the NASA backup system in which threecomputers do the same thing as a security measure. However,here there are multiple processors applying the same process todifferent data sets in parallel.Another configuration arranges processors in tandem, whereeach processor contributes one part to an overall computation.This approach is called pipelining, and is reminiscent of anassembly line. When this organization is applied to data, thefirst processor does the first task.
Then the second processorstarts working on the output from the first processor, while thefirst processor applies its computation to the next data set.Eventually, each processor is working on one phase of the job,each getting material or data from the previous stage ofprocessing, and each in turn handing over its work to the nextstage.The third approach is to have different processors doingdifferent things with different data.
This configuration allowsprocessors to work independently much of the time, butintroduces the problems of coordination among the processors.This leads to a configuration where the processors each havelocal memory and a shared memory. The processors use theshared memory for communication, and the configuration isthus called a shared memory configuration.Notes:Per track - на трек, на каждую дорожкуDrive partition - разбиение жесткого диска на логическиеразделыNASA (National Aeronautics and Space Administration)backup system - In the early days of manned space flights,NASA used a backup system composed of three mainframe48computers, each of which calculated exactly the same thing.
Ifone computer failed, there were still two computers carryingout the necessary calculations. If two computers failed, therewas still one computer left to do the necessary processing. Ifthree computers failed - fortunately, that never happened.PDA(PersonalDigitalComputer)карманныйперсональный компьютер (КПК)Assignments1. Translate the sentences from the text into Russian inwriting paying attention to the underlined words andphrases:1. Since most of main memory is volatile and limited, it isessential that there be other types of storage deviceswhere programs and data can be stored.2.
Rather than having concentric tracks, there is one trackthat spirals from the inside out.3. In order to make the transfer rate consistent throughoutthe disk, the rotation speed varies depending on theposition of the laser beam.4. Eventually, each processor is working on one phase ofthe job, each getting material or data from the previousstage of processing, and each in turn handing over itswork to the next stage.2.
Answer the following questions:1. Why is it essential that there be other types of storagedevices?2. Name the types of secondary storage devices.3. Describe the process of formatting a disk.4. What formats do CDs and DVDs come in?5. When is synchronous processing used?496. Why is pipelining compared to an assembly line?7. What is a shared memory configuration?3. Translate into English:С самого начала компьютерной эры существоваланеобходимость во все более и более производительныхсистемах. В основном это достигалось в результатеэволюции технологий производства компьютеров.
Наряду сэтим имели место попытки использовать несколькопроцессоров в одной вычислительной системе в расчете нато, что будет достигнуто соответствующее увеличениепроизводительности.Первойтакойпопыткой,осуществленной в начале 70-х годов, является ILLIAC IV.Сейчас имеется масса параллельных компьютеров ипроектов их реализации.Архитектуры параллельных компьютеров могутзначительно отличаться друг от друга.
Параллельныекомпьютеры состоят из трех основных компонентов:процессоры, модули памяти и коммутирующая сеть.Коммутирующая сеть соединяет процессоры друг с другоми иногда также с модулями памяти.4. Give the summary of the text using the key terms.Topics for essays (you might need additional information):The hierarchy of computer memory.The non-von Neumann architectures.50PROGRAMMING LANGUAGES AND PROGRAMLANGUAGE CONCEPTSBRIEF HISTORYLANGUAGESOFCOMPUTERPROGRAMMINGRead the following words and word combinations and usethem for understanding and translation of the text:to specify - уточнятьto morph into - трансформироваться в ...logical branching - логическое ветвлениеtedious - утомительныйto affect - влиятьshared program - разделенная (совместно используемая)программаhand-wired - установленный вручнуюarray - массивexplicit - точныйrestrictive - ограничивающийto handle - загружать, обрабатыватьto surpass - превосходитьparse tree - дерево синтаксического разбораdynamic variable - динамическая переменнаяto wind up - завершитьсяto implement - внедрятьsequentially - последовательноslider bar - скользящий маркер, бегунокduct tape - скотчoddball - эксцентричныйEver since the invention of Charles Babbage’s difference enginein 1822, computers have required a means of instructing themto perform a specific task - a program.
This means is known asa programming language. A programming language is a set of51rules that specify which sequences of symbols constitute aprogram, and what computation the program describes.A programming language is an abstraction mechanism. Itenables a programmer to specify a computation abstractly, andto let a program (usually called an assembler, compiler orinterpreter) implement the specification in the detailed formneededforexecutiononacomputer.Programming languages are the medium of expression in theart of computer programming.
An ideal programming languagewill make it easy for programmers to write programs clearly.Because programs are meant to be understood, modified, andmaintained over their lifetime, a good programming languagewill help others read programs and understand how they work.In evaluating programming languages, we must consider thetasks of designing, implementing, testing, and maintainingsoftware, asking how well each language supports each part ofthe software life cycle.Computer languages were first composed of a series of steps towire a particular program; these morphed into a series of stepskeyed into the computer and then executed; later theselanguages acquired advanced features such as logical branchingand object orientation.
The computer languages of the last fiftyyears have come in two stages, the first major languages andthe second major languages, which are in use today.In the beginning, Charles Babbage’s difference engine couldonly be made to execute tasks by changing the gears whichexecuted the calculations. Thus, the earliest form of a computerlanguage was physical motion. Eventually, physical motionwas replaced by electrical signals when the US Governmentbuilt the ENIAC in 1942.
It followed many of the sameprinciples of Babbage’s engine and hence, could only be“programmed” by presetting switches and rewiring the entiresystem for each new “program” or calculation. This processproved to be very tedious.In 1945, John Von Neumann was working at the Institute forAdvanced Study. He developed two important concepts that52directly affected the path of computer programming languages.The first was known as “shared-program technique”. Thistechnique stated that the actual computer hardware should besimple and not need to be hand-wired for each program.Instead, complex instructions should be used to control thesimple hardware, allowing it to be reprogrammed much faster.The second concept was also extremely important to thedevelopment of programming languages.
Von Neumann calledit “conditional control transfer”. This idea gave rise to thenotion of subroutines, or small blocks of code that could bejumped to in any order, instead of a single set ofchronologically ordered steps for the computer to take. Thesecond part of the idea stated that computer code should beable to branch based on logical statements such as IF(expression) THEN, and looped such as with a FOR statement.“Conditional control transfer” gave rise to the idea of“libraries,” which are blocks of code that can be reused overand over.In 1949, a few years after Von Neumann’s work, the languageShort Code appeared.
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