COMPUTER ELEMENTARY final 1

function of memory in your computer. It helps the CPU access things in memory to avoid running your computer down accessing them from their original place of storage.

The average computer comes with four types of primary memory: Level one and two cache, RAM, virtual and hard disk memory. When your computer tries to access memory, it uses these different levels to access, open and utilize computer processes. The hard disk is one of the cheapest types of memory. It is a permanent storage device, but it can consume too much time to open and read data from it. So, virtual memory comes into play in conjunction with the CPU to help read the hard disk and make it a bit quicker to read the unit.

RAM

Computer RAM (Random Access Memory) is the best known form of memory your computer uses. Every file or application opened is placed in RAM. Any information the computer needs or uses becomes part of a continuous cycle where the CPU requests data from RAM, processes it and then writes new data back to RAM. This can happen millions of times a second. However, this is usually just for temporary file storage, so unless the data is saved somewhere, it is deleted when the files or applications are closed. It is volatile memory.

Most modern semiconductor volatile memory is either Static RAM (see SRAM) or dynamic RAM (see DRAM). SRAM retains its contents as long as the power is connected and is easy to interface to. Dynamic RAM is more complicated to interface to and control and needs regular refresh cycles to prevent its contents being lost. SRAM is not worthwhile for desktop system memory, where DRAM dominates, but is used for their cache memories.

Recent advances in memory technology have included the development of magnetic RAM (MRAM). The MRAM is a memory device for reading and writing information wherein multi-layer ferromagnetic thin films is used by sensing current variations according to a magnetization direction of the respective thin films. MRAM stores information magnetically, so it does not require a constant power supply. This quality is known as non-volatility. MRAM can offer all the advantages in speed and size that volatile memory offers and brings the added

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advantage of being non-volatile and, in some architectural configurations, cheaper to manufacture. MRAM can operate at speeds similar to either SRAM or DRAM, thus allowing it to be utilized within main memory. The MRAM has a high speed and low power consumption, and allows high integration density due to its unique properties of the magnetic thin film, and also performs a nonvolatile memory operation such as a flash memory.

The RAM helps sync types of memory together, but since they do not directly connect and interact with the CPU, the cache levels help fuse everything together so that your computer runs faster when accessing data at different intervals. While there is much more to memory than just these facets, this is just a basic overview of how it all works together to keep your computer running. So, the next time you think your computer is slow, perhaps, it is time for a memory upgrade.

Cache memory

RAM is not fast enough to keep up with the CPU. Cache Memory is used inbetween the CPU and the RAM and holds the most frequently used data or instructions to be processed. There are three different grades of Cache. Some systems will only have level 1 and level 2. More advanced systems will include the level 3.

Level 1 (L1) is the primary and is on or very close to the processor. Level 2 (L2) is second closest to the CPU and is more common to be on the motherboard. Level 3 (L3) is the most advanced cache and will speed up the memory even further. Cache memory is used for the most frequently used data and instructions.

Level one cache utilizes small amounts of memory in the CPU whereas level two hides out in a chip near the CPU. It actually connects to the CPU itself and helps to keep it from overclocking when accessing its own memory.

Hard drive

A Hard Drive is a form of computer memory that allows you to permanently store data. This is where all of your permanent files and programs are stored. On computers running with Microsoft windows the Hard Drive is often called C- Drive. The size of a Hard Drive is typically measured in gigabytes.

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There is another division of the types of memory into primary and secondary. Primary memory is the memory that can be directly accessed by the CPU which constantly interacts with it, retrieves data stored therein, goes through instructions and execute them as per the requirement. All the information, data and application are loaded there in uniform manner.

Secondary memory is not directly accessible to the CPU. This memory does not lose the data when the system is powered off. The most familiar form of secondary memory that is widely used is external Hard Disk. Some examples of secondary memory are USB sticks, floppy drives and Zip drives.

Virtual memory

Virtual memory is a system where all physical memory is controlled by the operating system. When a program needs memory, it requests it from the operating system. The operating system then decides what physical location to place the memory in. Virtual memory typically comes into place when applications are too large for the RAM to handle. The operating system uses the hard drive to temporarily store information and take it back when needed. This is normally a lot slower than actual RAM and can possibly degrade performance if used to heavily.

This offers several advantages. Computer programmers no longer need to worry about where the memory is physically stored or whether the user's computer will have enough memory. It also allows multiple types of memory to be used. For example, some memory can be stored in physical RAM chips while other memory is stored on a hard drive. This drastically increases the amount of memory available to programs. The operating system will place actively used memory in physical RAM, which is much faster than hard disks. When the amount of RAM is not sufficient to run all the current programs, it can result in a situation where the computer spends more time moving memory from RAM to disk and back than it does accomplishing tasks; this is known as thrashing.

Systems that employ virtual memory:

•use hardware memory more efficiently than systems without virtual memory

•make the programming of applications easier by:

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•delegating to the kernel the burden of managing the memory hierarchy; there is no need for the program to handle overlays explicitly.

•obviating the need to relocate program code or to access memory with relative addressing.

Memory virtualization is a generalization of the concept of virtual memory. Virtual memory systems usually include protected memory, but this is not always the case.

Protected memory

Protected memory is a system where each program is given an area of memory to use and is not permitted to go outside that range. Use of protected memory greatly enhances both the reliability and security of a computer system.

Without protected memory, it is possible that a bug in one program will alter the memory used by another program. This will cause that other program to run off of corrupted memory with unpredictable results. If the operating system's memory is corrupted, the entire computer system may crash and need to be rebooted. At times programs intentionally alter the memory used by other programs. This is done by viruses and malware to take over computers.

Protected memory assigns programs their own areas of memory. If the operating system detects that a program has tried to alter memory that doesn't belong to it, the program is terminated. This way, only the offending program crashes, and other programs are not affected by the error.

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1.What is computer memory? What types do you know?

2.What is RAM? How does it operate?

3.What types of RAM do you know? What is the difference between them?

4.Can we say that technological advance will make RAM non-volatile?

5.What is Hard Disc Memory? What is it necessary for?

6.What is Cache memory? What levels do you know?

7.How do all types of memory interact?

8.What is the difference between the secondary and the primary memory?

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9. How does virtual memory differ from other types? What is it very useful?

10.What is protected memory?

Exercise 2: Find in the main text English equivalents for the following words or word combinations.

Exercise 3. Find Russian equivalents for the following words or word combinations from the text.

Exercise 4. State whether it is true or false. Correct false statements, if any.

1.There are different types of memory such as RAM, ROM, BIOS, Cache Memory, virtual memory, etc.

2.Computer memory is always temporary.

3.Since every action on your computer requires some form of memory, whether it is actual or virtual memory.

4.Every file or application opened is placed in RAM.

5.The CPU requests data from RAM, processes it and then saves new data back to RAM.

6.There are two types of RAM: SRAM and DRAM.

7.DRAM is easy to interface, so it dominates.

8.MRAM, being volatile, can offer all the advantages in speed and size that any volatile memory offers.

9.Cache Memory holds the most frequently used data or instructions to be

processed.

10.There are two levels of Cache memory that are located on the motherboard to speed up the processes.

11.Virtual memory is a device to control all the system.

12.When a program needs memory it requests the CPU and the CPU locates the data in the RAM.

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13.If the operating system detects that a program has tried to alter memory that doesn't belong to it, the program is removed.

Exercise 5. Complete the sentences using the information from the text

1.The most common types of memory average consumers know about are … .

2.The primary function of memory in your computer … .

3.Every file or application opened is placed in RAM. Any information the computer needs or uses becomes part of a continuous cycle where … .

4. . MRAM stores information magnetically, so … .

5.Cache Memory is used in-between the CPU and the RAM and … .

6.Primary memory is the memory that … .

7.There is another division of memory into… .

8.The most familiar forms of secondary memory are… .

9.Virtual memory typically comes into place when … .

10.The operating system will place actively used memory in physical RAM because… .

11.When the amount of RAM is not sufficient to run all the current programs, it can result in a situation where… .

12.If the operating system's memory is corrupted… .

13.At times programs, like viruses and malware, intentionally … .

Exercise 6. Read the text. Answer the questions.

Text 2

Magnetic Storage

Magnetic storage devices store data by magnetizing particles on a disk or tape.

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A floppy disk is so called because it consists of a flexible sheet of plastic, coated with iron oxide – a magnetizable material. A floppy disk drive spins at 360 revolutions per minute (rpm), so it's relatively slow. However, a hard drive spins at over

7,200 rpm and stores data on a stack of metal rotating disks called platters. This means you can store much more data and retrieve information much faster.

New disks need to be formatted before you can use them, unless they come preformatted from the manufacturer. When the disk is formatted, the operating system (OS) organizes the disk surface into circular tracks and divides each track into sectors. The OS creates a directory which will record the specific location of files. When you save a file, the OS moves the read/write head of the drive towards empty sectors, records the data and writes an entry for the directory. Later on, when you open that file, the OS looks for its entry in the directory, moves the read/write heads to the correct sector, and reads the file in the RAM area. However, formatting erases any existing files on a disk, so do not format disks on which data that you don't want to lose is stored.

The OS allows you to create one or more partitions on your hard drive, in effect dividing it into several logical parts. Partitions let you install more than one operating system (e.g. Windows and Linux) on your computer. You may also decide to split your hard drive because you want to store the OS and programs on one partition and your data files on another; this allows you to reinstall the OS when a problem occurs, without affecting the data partition.

The average time required for the read/write heads to move and find data is called seek time (or access time) and it is measured in milliseconds (ms); most hard drives have a seek time of 7 to 14 ms. Don't confuse this with transfer rate - the average speed required to transmit data from the disk to the CPU, measured in megabytes per second.

How to protect your hard drive

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•Don’t hit or move the computer while the hard drive is spinning. Hard drives are very sensitive to vibration and shocks, especially when they are operating; when the read/write head touches the rotating disk, it can scratch and damage the disk surface. This is known as head crash.

•You shouldn't turn your computer off and on quickly. Wait at least ten seconds to ensure that the drive has stopped spinning.

•Check your hard drive regularly for logical and physical errors. To check and repair a drive, you can use a disk diagnosis utility like Windows ScanDisk.

•To minimize the risk of data loss or corruption, you should install an up-to-date

virus scanner. You should also back up your hard drive regularly.

The future of hard drives may be hybrid hard drives. Hybrid hard drives combine a magnetic hard disk and flash memory into one device. This allows computers to boot, or start, more quickly, and also reduces power consumption.

Optical discs and drives

Optical discs can store data at much higher densities than magnetic disks. They are therefore ideal for multimedia applications where images, animation and sound occupy a lot of disc space. Furthermore, optical discs are not affected by magnetic fields, meaning that they are secure and stable, and can be transported through airport metal detectors without damaging the data. However, optical drives are slower than hard drives.

At first sight, a DVD is similar to a CD. Both discs are 120 mm in diameter and 1.2 mm thick. They also both use a laser beam to read data. However, they are very different in internal structure and data capacity. In a DVD, the tracks are very close together, thus allowing more tracks. The pits in which data is stored are also smaller, so there are more pits per track. As a result, a CD can hold 650-700MB, whereas a basic DVD can hold 4.7GB. In addition, a DVD can be double-sided and dual layer, with a capacity of 17GB.

CDs come in three different formats:

•CD-ROMs (read-only memory) are read-only units, meaning you cannot change the data stored on them (for example, a dictionary or a game).

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•CD-R (recordable) discs are write-once devices which let you duplicate music CDs and other data CDs.

•CD-RW (rewritable) discs enable you to write onto them many times, just like

a hard disk.

DVDs also come in several formats:

•DVD-ROMs are used in DVD computer drives. They allow for data archiving as well as interactive content (for example, an encyclopedia or a movie).

•DVD-R or DVD+R can only be recorded on once.

•DVD-RW or DVD+RW discs can be erased and reused many times. They are used to back up data files and to record audio and video.

The DVD drive used in computers is also called a DVD burner because it records information by burning via a laser to a blank DVD disc. However, a DVD recorder typically refers to a unit which resembles a video cassette recorder. New DVD recorders can play all CD and DVD formats. There are also portable DVD players - handheld devices which let you watch movies or TV, play games and listen to music, wherever you are. They come with a built-in DVD drive and widescreen (rectangular 16:9 format) LCD display. They usually support multi-format playback - that is, they can play many file formats, including DVD-video, DivX, CD audio discs, MP3 music and JPEG images.

HD-DVD and Blu-ray discs are two competing formats that are expected to replace current DVD as the standard for watching movies at home. Toshiba, Microsoft and the DVD Forum support the High Definition-DVD (HD-DVD). Sony, Panasonic, Samsung, JVC and many movie studios are behind the Blu-ray format.

A Blu-ray disc has a capacity of 25GB (single layer), 50GB (dual layer) and 100GB (four layer). Unlike DVDs, which use a red laser to read and write data, Blu-ray uses a blue-violet laser, hence its name. Blu-ray discs can record and play back high-definition television and digital audio, as well as computer data.

Flash memory

Flash memory is a type of non-volatile memory that can be electronically erased and reprogrammed. Its name was invented by Toshiba to express how much faster it could be erased -'in a flash' which means 'very quickly'.

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