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Development of Peer-to-Peer Network System

Disclaimer: This work has been submitted by a student. This is not an example of the work written by our professional academic writers. You can view samples of our professional work here.

Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of UK Essays.

Published: Fri, 02 Mar 2018

Procedures which we are followed to success this project.

Task 01 – Familiarizing with the equipments & preparing an action plan.

Task 02 – Prepare the work area.

Task 03 – Fixed the hardware equipments and assemble three PCs.

Task 04 – Install NICs for each and every PC.

Task 05 – Cabling three computers and configure the peer to peer network with using hub or switch.

Task 06 – Install Windows operating system to each and every PC.

Task 07 – Install and configure the printer on one of the PCs.

Task 08 – Share printer with other PCs in the LAN.

Task 09 – Establish one shared folder

Task 10 – Create a test document on one of the PCs and copy the files to each of the other PCs in network.

Task 11 – Test the printer by getting the test document from each of the networked PCs.

Time allocation for the tasks.

Task No. Time allocation

Task 01 1 hour

Task 02 30 minutes

Task 03 1 ½ hour

Task 04 1 ½ hour

Task 05 1 ½ hour

Task 06 3 hour

Task 07 15 minutes

Task 08 15 minutes

Task 09 15 minutes

Task 10 10 minutes

Task 11 05 minutes

Total time allocation – 10 hours

Physical structure of proposed Peer to Peer network system.

In peer to peer network there are no dedicated servers or hierarchy among the computers. The user must take the decisions about who access this network.

Processors

In 1945, the idea of the first computer with a processing unit capable of performing different tasks was published by John von Neumann. The computer was called the EDVAC and was finished in 1949. These first primitive computer processors, such as the EDVAC and the Harvard Mark I, were incredibly bulky and large. Hundreds of CPUs were built into the machine to perform the computers tasks.

Starting in the 1950s, the transistor was introduced for the CPU. This was a vital improvement because they helped remove much of the bulky material and wiring and allowed for more intricate and reliable CPU’s. The 1960s and 1970s brought about the advent of microprocessors. These were very small, as the length would usually be recorded in nanometers, and were much more powerful. Microprocessors helped this technology become much more available to the public due to their size and affordability. Eventually, companies like Intel and IBM helped alter microprocessor technology into what we see today. The computer processor has evolved from a big bulky contraption to a minuscule chip.

Computer processors are responsible for four basic operations. Their first job is to fetch the information from a memory source. Subsequently, the CPU is to decode the information to make it usable for the device in question. The third step is the execution of the information, which is when the CPU acts upon the information it has received. The fourth and final step is the write back. In this step, the CPU makes a report of the activity and stores it in a log.

Two companies are responsible for a vast majority of CPUs sold all around the world. Intel Corporation is the largest CPU manufacturer in the world and is the maker of a majority of the CPUs found in personal computers. Advanced Micro Devices, Inc., known as AMD, has in recent years been the main competitor for Intel in the CPU industry.

The CPU has greatly helped the world progress into the digital age. It has allowed a number of computers and other machines to be produced that are very important and essential to our global society. For example, many of the medical advances made today are a direct result of the ability of computer processors. As CPUs improve, the devices they are used in will also improve and their significance will become even greater.

VGA

The term Video Graphics Array (VGA) refers specifically to the display hardware first introduced with the IBM PS/2 line of computers in 1987,[1] but through its widespread adoption has also come to mean either an analogue computer display standard, the 15-pin D-sub miniature VGA connector or the 640×480 resolution itself. While this resolution has been superseded in the personal computer market, it is becoming a popular resolution on mobile devices.

Video Graphics Array (VGA) was the last graphical standard introduced by IBM that the majority of PC clone manufacturers conformed to, making it today (as of 2009) the lowest common denominator that all PC graphics hardware supports, before a device-specific driver is loaded into the computer. For example, the MS-Windows splash screen appears while the machine is still operating in VGA mode, which is the reason that this screen always appears in reduced resolution and colour depth.

VGA was officially superseded by IBM’s XGA standard, but in reality it was superseded by numerous slightly different extensions to VGA made by clone manufacturers that came to be known collectively as “Super VGA”.

VGA is referred to as an “array” instead of an “adapter” because it was implemented from the start as a single chip (an ASIC), replacing the Motorola 6845 and dozens of discrete logic chips that covered the full-length ISA boards of the MDA, CGA, and EGA. Its single-chip implementation also allowed the VGA to be placed directly on a PC’s motherboard with a minimum of difficulty (it only required video memory, timing crystals and an external RAMDAC), and the first IBM PS/2 models were equipped with VGA on the motherboard.

RAM

Random-access memory (usually known by its acronym, RAM) is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order (i.e., at random). The word random thus refers to the fact that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.

By contrast, storage devices such as tapes, magnetic discs and optical discs rely on the physical movement of the recording medium or a reading head. In these devices, the movement takes longer than data transfer, and the retrieval time varies based on the physical location of the next item. The word RAM is often associated with volatile types of memory (such as DRAM memory modules), where the information is lost after the power is switched off. Many other types of memory are RAM, too, including most types of ROM and flash memory called NOR-Flash.

An early type of widespread writable random-access memory was the magnetic core memory, developed from 1949 to 1952, and subsequently used in most computers up until the development of the static and dynamic integrated RAM circuits in the late 1960s and early 1970s. Before this, computers used relays, delay line memory, or various kinds of vacuum tube arrangements to implement “main” memory functions (i.e., hundreds or thousands of bits); some of which were random access, some not. Latches built out of vacuum tube triodes, and later, out of discrete transistors, were used for smaller and faster memories such as registers and random-access register banks. Modern types of writable RAM generally store a bit of data in either the state of a flip-flop, as in SRAM (static RAM), or as a charge in a capacitor (or transistor gate), as in DRAM (dynamic RAM), EPROM, EEPROM and Flash. Some types have circuitry to detect and/or correct random faults called memory errors in the stored data, using parity bits or error correction codes. RAM of the read-only type, ROM, instead uses a metal mask to permanently enable/disable selected transistors, instead of storing a charge in them.

As both SRAM and DRAM are volatile, other forms of computer storage, such as disks and magnetic tapes, have been used as persistent storage in traditional computers. Many newer products instead rely on flash memory to maintain data when not in use, such as PDAs or small music players. Certain personal computers, such as many rugged computers and net books, have also replaced magnetic disks with flash drives. With flash memory, only the NOR type is capable of true random access, allowing direct code execution, and is therefore often used instead of ROM; the lower cost NAND type is commonly used for bulk storage in memory cards and solid-state drives.

Similar to a microprocessor, a memory chip is an integrated circuit (IC) made of millions of transistors and capacitors. In the most common form of computer memory, dynamic random access memory (DRAM), a transistor and a capacitor are paired to create a memory cell, which represents a single bit of data. The transistor acts as a switch that lets the control circuitry on the memory chip read the capacitor or change its state.

Types of RAM

Top L-R, DDR2 with heat-spreader, DDR2 without heat-spreader, Laptop DDR2, DDR, Laptop DDR

1 Megabit chip – one of the last models developed by VEB Carl Zeiss Jena in 1989

Many computer systems have a memory hierarchy consisting of CPU registers, on-die SRAM caches, external caches, DRAM, paging systems, and virtual memory or swap space on a hard drive. This entire pool of memory may be referred to as “RAM” by many developers, even though the various subsystems can have very different access times, violating the original concept behind the random access term in RAM. Even within a hierarchy level such as DRAM, the specific row, column, bank, rank, channel, or interleave organization of the components make the access time variable, although not to the extent that rotating storage media or a tape is variable. The overall goal of using a memory hierarchy is to obtain the higher possible average access performance while minimizing the total cost of entire memory system. (Generally, the memory hierarchy follows the access time with the fast CPU registers at the top and the slow hard drive at the bottom.)

In many modern personal computers, the RAM comes in an easily upgraded form of modules called memory modules or DRAM modules about the size of a few sticks of chewing gum. These can quickly be replaced should they become damaged or too small for current purposes. As suggested above, smaller amounts of RAM (mostly SRAM) are also integrated in the CPU and other ICs on the motherboard, as well as in hard-drives, CD-ROMs, and several other parts of the computer system.

Hard Disk

A hard disk drive (often shortened as hard disk, hard drive, or HDD) is a non-volatile storage device that stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Strictly speaking, “drive” refers to the motorized mechanical aspect that is distinct from its medium, such as a tape drive and its tape, or a floppy disk drive and its floppy disk. Early HDDs had removable media; however, an HDD today is typically a sealed unit (except for a filtered vent hole to equalize air pressure) with fixed media.

HDDs (introduced in 1956 as data storage for an IBM accounting computer) were originally developed for use with general purpose computers. During the 1990s, the need for large-scale, reliable storage, independent of a particular device, led to the introduction of embedded systems such as RAIDs, network attached storage (NAS) systems, and storage area network (SAN) systems that provide efficient and reliable access to large volumes of data. In the 21st century, HDD usage expanded into consumer applications such as camcorders, cell phones (e.g. the Nokia N91), digital audio players, digital video players, digital video recorders, personal digital assistants and video game consoles.

HDDs record data by magnetizing ferromagnetic material directionally, to represent either a 0 or a 1 binary digit. They read the data back by detecting the magnetization of the material. A typical HDD design consists of a spindle that holds one or more flat circular disks called platters, onto which the data are recorded. The platters are made from a non-magnetic material, usually aluminium alloy or glass, and are coated with a thin layer of magnetic material, typically 10-20 nm in thickness with an outer layer of carbon for protection. Older disks used iron (III) oxide as the magnetic material, but current disks use a cobalt-based alloy.

The platters are spun at very high speeds. Information is written to a platter as it rotates past devices called read-and-write heads that operate very close (tens of nanometres in new drives) over the magnetic surface. The read-and-write head is used to detect and modify the magnetization of the material immediately under it. There is one head for each magnetic platter surface on the spindle, mounted on a common arm. An actuator arm (or access arm) moves the heads on an arc (roughly radially) across the platters as they spin, allowing each head to access almost the entire surface of the platter as it spins. The arm is moved using a voice coil actuator or in some older designs a stepper motor.

The magnetic surface of each platter is conceptually divided into many small sub-micrometre-sized magnetic regions, each of which is used to encode a single binary unit of information. Initially the regions were oriented horizontally, but beginning about 2005, the orientation was changed to perpendicular. Due to the polycrystalline nature of the magnetic material each of these magnetic regions is composed of a few hundred magnetic grains. Magnetic grains are typically 10 nm in size and each form a single magnetic domain. Each magnetic region in total forms a magnetic dipole which generates a highly localized magnetic field nearby. A write head magnetizes a region by generating a strong local magnetic field. Early HDDs used an electromagnet both to magnetize the region and to then read its magnetic field by using electromagnetic induction. Later versions of inductive heads included metal in Gap (MIG) heads and thin film heads. As data density increased, read heads using magnetoresistance (MR) came into use; the electrical resistance of the head changed according to the strength of the magnetism from the platter. Later development made use of spintronics; in these heads, the magnetoresistive effect was much greater than in earlier types, and was dubbed “giant” magnetoresistance (GMR). In today’s heads, the read and write elements are separate, but in close proximity, on the head portion of an actuator arm. The read element is typically magneto-resistive while the write element is typically thin-film inductive.[8]

HD heads are kept from contacting the platter surface by the air that is extremely close to the platter; that air moves at, or close to, the platter speed. The record and playback head are mounted on a block called a slider, and the surface next to the platter is shaped to keep it just barely out of contact. It’s a type of air bearing.

In modern drives, the small size of the magnetic regions creates the danger that their magnetic state might be lost because of thermal effects. To counter this, the platters are coated with two parallel magnetic layers, separated by a 3-atom-thick layer of the non-magnetic element ruthenium, and the two layers are magnetized in opposite orientation, thus reinforcing each other.[9] Another technology used to overcome thermal effects to allow greater recording densities is perpendicular recording, first shipped in 2005,[10] as of 2007 the technology was used in many HDDs.

The grain boundaries turn out to be very important in HDD design. The reason is that, the grains are very small and close to each other, so the coupling between adjacent grains is very strong. When one grain is magnetized, the adjacent grains tend to be aligned parallel to it or demagnetized. Then both the stability of the data and signal-to-noise ratio will be sabotaged. A clear grain perpendicular boundary can weaken the coupling of the grains and subsequently increase the signal-to-noise ratio. In longitudinal recording, the single-domain grains have uniaxial anisotropy with easy axes lying in the film plane. The consequence of this arrangement is that adjacent magnets repel each other. Therefore the magnetostatic energy is so large that it is difficult to increase areal density. Perpendicular recording media, on the other hand, has the easy axis of the grains oriented to the disk plane. Adjacent magnets attract to each other and magnetostatic energy are much lower. So, much higher areal density can be achieved in perpendicular recording. Another unique feature in perpendicular recording is that a soft magnetic underlayer are incorporated into the recording disk.This underlayer is used to conduct writing magnetic flux so that the writing is more efficient. This will be discussed in writing process. Therefore, a higher anisotropy medium film, such as L10-FePt and rare-earth magnets, can be used.

Opened hard drive with top magnet removed, showing copper head actuator coil (top right).

A hard disk drive with the platters and motor hub removed showing the copper colored stator coils surrounding a bearing at the center of the spindle motor. The orange stripe along the side of the arm is a thin printed-circuit cable. The spindle bearing is in the center.

A typical hard drive has two electric motors, one to spin the disks and one to position the read/write head assembly. The disk motor has an external rotor attached to the platters; the stator windings are fixed in place. The actuator has a read-write head under the tip of its very end (near center); a thin printed-circuit cable connects the read-write head to the hub of the actuator. A flexible, somewhat ‘U’-shaped, ribbon cable, seen edge-on below and to the left of the actuator arm in the first image and more clearly in the second, continues the connection from the head to the controller board on the opposite side.

The head support arm is very light, but also rigid; in modern drives, acceleration at the head reaches 250 Gs.

The silver-colored structure at the upper left of the first image is the top plate of the permanent-magnet and moving coil motor that swings the heads to the desired position (it is shown removed in the second image). The plate supports a thin neodymium-iron-boron (NIB) high-flux magnet. Beneath this plate is the moving coil, often referred to as the voice coil by analogy to the coil in loudspeakers, which is attached to the actuator hub, and beneath that is a second NIB magnet, mounted on the bottom plate of the motor (some drives only have one magnet).

The voice coil, itself, is shaped rather like an arrowhead, and made of doubly-coated copper magnet wire. The inner layer is insulation, and the outer is thermoplastic, which bonds the coil together after its wound on a form, making it self-supporting. The portions of the coil along the two sides of the arrowhead (which point to the actuator bearing center) interact with the magnetic field, developing a tangential force that rotates the actuator. Current flowing racially outward along one side of the arrowhead and racially inward on the other produces the tangential force. (See magnetic field Force on a charged particle.) If the magnetic field were uniform, each side would generate opposing forces that would cancel each other out. Therefore the surface of the magnet is half N pole, half S pole, with the radial dividing line in the middle, causing the two sides of the coil to see opposite magnetic fields and produce forces that add instead of canceling. Currents along the top and bottom of the coil produce radial forces that do not rotate the head.

Floppy disk

A floppy disk is a data storage medium that is composed of a disk of thin, flexible (“floppy”) magnetic storage medium encased in a square or rectangular plastic shell. Floppy disks are read and written by a floppy disk drive or FDD, the initials of which should not be confused with “fixed disk drive,” which is another term for a (non removable) type of hard disk drive. Invented by IBM, floppy disks in 8-inch (200mm), 5¼-inch (133.35mm), and 3½-inch (90mm) formats enjoyed many years as a popular and ubiquitous form of data storage and exchange, from the mid-1970s to the late 1990s. While floppy disk drives still have some limited uses, especially with legacy industrial computer equipment,[2] they have now been largely superseded by USB flash drives, external hard drives, CDs, DVDs, and memory cards (such as Secure Digital).

5¼-inch disk had a large circular hole in the center for the spindle of the drive and a small oval aperture in both sides of the plastic to allow the heads of the drive to read and write the data. The magnetic medium could be spun by rotating it from the middle hole. A small notch on the right hand side of the disk would identify whether the disk was read-only or writable, detected by a mechanical switch or photo transistor above it. Another LED/phototransistor pair located near the center of the disk could detect a small hole once per rotation, called the index hole, in the magnetic disk. It was used to detect the start of each track, and whether or not the disk rotated at the correct speed; some operating systems, such as Apple DOS, did not use index sync, and often the drives designed for such systems lacked the index hole sensor. Disks of this type were said to be soft sector disks. Very early 8-inch and 5¼-inch disks also had physical holes for each sector, and were termed hard sector disks. Inside the disk were two layers of fabric designed to reduce friction between the medium and the outer casing, with the medium sandwiched in the middle. The outer casing was usually a one-part sheet, folded double with flaps glued or spot-welded together. A catch was lowered into position in front of the drive to prevent the disk from emerging, as well as to raise or lower the spindle (and, in two-sided drives, the upper read/write head).

The 8-inch disk was very similar in structure to the 5¼-inch disk, with the exception that the read-only logic was in reverse: the slot on the side had to be taped over to allow writing.

The 3½-inch disk is made of two pieces of rigid plastic, with the fabric-medium-fabric sandwich in the middle to remove dust and dirt. The front has only a label and a small aperture for reading and writing data, protected by a spring-loaded metal or plastic cover, which is pushed back on entry into the drive.

Newer 5¼-inch drives and all 3½-inch drives automatically engages when the user inserts a disk, and disengages and ejects with the press of the eject button. On Apple Macintosh computers with built-in floppy drives, the disk is ejected by a motor (similar to a VCR) instead of manually; there is no eject button. The disk’s desktop icon is dragged onto the Trash icon to eject a disk.

The reverse has a similar covered aperture, as well as a hole to allow the spindle to connect into a metal plate glued to the medium. Two holes bottom left and right, indicate the write-protect status and high-density disk correspondingly, a hole meaning protected or high density, and a covered gap meaning write-enabled or low density. A notch top right ensures that the disk is inserted correctly, and an arrow top left indicates the direction of insertion. The drive usually has a button that, when pressed, will spring the disk out at varying degrees of force. Some would barely make it out of the disk drive; others would shoot out at a fairly high speed. In a majority of drives, the ejection force is provided by the spring that holds the cover shut, and therefore the ejection speed is dependent on this spring. In PC-type machines, a floppy disk can be inserted or ejected manually at any time (evoking an error message or even lost data in some cases), as the drive is not continuously monitored for status and so programs can make assumptions that do not match actual status.

With Apple Macintosh computers, disk drives are continuously monitored by the OS; a disk inserted is automatically searched for content, and one is ejected only when the software agrees the disk should be ejected. This kind of disk drive (starting with the slim “Twiggy” drives of the late Apple “Lisa”) does not have an eject button, but uses a motorized mechanism to eject disks; this action is triggered by the OS software (e.g., the user dragged the “drive” icon to the “trash can” icon). Should this not work (as in the case of a power failure or drive malfunction), one can insert a straightened paper clip into a small hole at the drive’s front, there by forcing the disk to eject (similar to that found on CD/DVD drives). Some other computer designs (such as the Commodore Amiga) monitor for a new disk continuously but still have push-button eject mechanisms.

The 3-inch disk, widely used on Amstrad CPC machines, bears much similarity to the 3½-inch type, with some unique and somewhat curious features. One example is the rectangular-shaped plastic casing, almost taller than a 3½-inch disk, but narrower, and more than twice as thick, almost the size of a standard compact audio cassette. This made the disk look more like a greatly oversized present day memory card or a standard PC card notebook expansion card rather than a floppy disk. Despite the size, the actual 3-inch magnetic-coated disk occupied less than 50% of the space inside the casing, the rest being used by the complex protection and sealing mechanisms implemented on the disks. Such mechanisms were largely responsible for the thickness, length and high costs of the 3-inch disks. On the Amstrad machines the disks were typically flipped over to use both sides, as opposed to being truly double-sided. Double-sided mechanisms were available but rare.

USB Ports

Universal Serial Bus connectors on the back. These USB connectors let you attach everything from mice to printers to your computer quickly and easily. The operating system supports USB as well, so the installation of the device drivers is quick and easy, too. Compared to other ways of connecting devices to your computer, USB devices are incredibly simple we will look at USB ports from both a user and a technical standpoint. You will learn why the USB system is so flexible and how it is able to support so many devices so easily Anyone who has been around computers for more than two or three years know the problem that the Universal Serial Bus is trying to solve — in the past, connecting devices to computers has been a real headache!

  • Printers connected to parallel printer ports, and most computers only came with one. Things like Zip drives, which need a high-speed connection into the computer, would use the parallel port as well, often with limited success and not much speed.
  • Modems used the serial port, but so did some printers and a variety of odd things like Palm Pilots and digital cameras. Most computers have at most two serial ports, and they are very slow in most cases.
  • Devices that needed faster connections came with their own cards, which had to fit in a card slot inside the computer’s case. Unfortunately, the number of card slots is limited and you needed a Ph.D. to install the software for some of the cards.

The goal of USB is to end all of these headaches. The Universal Serial Bus gives you a single, standardized, easy-to-use way to connect up to 127 devices to a computer. Just about every peripheral made now comes in a USB version. A sample list of USB devices that you can buy today includes:

  • Printers
  • Scanners
  • Mice
  • Joysticks
  • Flight yokes
  • Digital cameras
  • Webcams
  • Scientific data acquisition devices
  • Modems
  • Speakers
  • Telephones
  • Video phones
  • Storage devices such as Zip drives
  • Network connections

In the next section, we’ll look at the USB cables and connectors that allow your computer to communicate with these devices.

Parallel port

A parallel port is a type of interface found on computers (personal and otherwise) for connecting various peripherals. It is also known as a printer port or Centronics port. The IEEE 1284 standard defines the bi-directional version of the port.

Before the advent of USB, the parallel interface was adapted to access a number of peripheral devices other than printers. Probably one of the earliest devices to use parallel were dongles used as a hardware key form of software copy protection. Zip drives and scanners were early implementations followed by external modems, sound cards, webcams, gamepads, joysticks and external hard disk drives and CD-ROM drives. Adapters were available to run SCSI devices via parallel. Other devices such as EPROM programmers and hardware controllers could be connected parallel.

At the consumer level, the USB interface—and in some cases Ethernet—has effectively replaced the parallel printer port. Many manufacturers of personal computers and laptops consider parallel to be a legacy port and no longer include the parallel interface. USB to parallel adapters are available to use parallel-only printers with USB-only systems. However, due to the simplicity of its implementation, it is often used for interfacing with custom-made peripherals. In versions of Windows that did not use the Windows NT kernel (as well as DOS and some other operating systems)

Keyboard

Keyboard, in computer science, a keypad device with buttons or keys that a user presses to enter data characters and commands into a computer. They are one of the fundamental pieces of personal computer (PC) hardware, along with the central processing unit (CPU), the monitor or screen, and the mouse or other cursor device.

The most common English-language key pattern for typewriters and keyboards is called QWERTY, after the layout of the first six letters in the top row of its keys (from left to right). In the late 1860s, American inventor and printer Christopher Shoals invented the modern form of the typewriter. Shoals created the QWERTY keyboard layout by separating commonly used letters so that typists would type slower and not jam their mechanical typewriters. Subsequent generations of typists have learned to type using QWERTY keyboards, prompting manufacturers to maintain this key orientation on typewriters.

Computer keyboards copied the QWERTY key layout and have followed the precedent set by typewriter manufacturers of keeping this convention. Modern keyboards connect with the computer CPU by cable or by infrared transmitter. When a key on the keyboard is pressed, a numeric code is sent to the keyboard’s driver software and to the computer’s operating system software. The driver translates this data into a specialized command that the computer’s CPU and application programs understand. In this way, users may enter text, commands, numbers, or other data. The term character is generally reserved for letters, numbers, and punctuation, but may also include control codes, graphical symbols, mathematical symbols, and graphic images.

Almost all standard English-language keyboards have keys for each character of the American Standard Code for Information Interchange (ASCII) character set, as well as various function keys. Most computers and applications today use seven or eight data bits for each character. For example, ASCII code 65 is equal to the letter A. The function keys generate short, fixed sequences of character codes that instruct application programs running on the computer to perform certain actions. Often, keyboards also have directional buttons for moving the screen cursor, separate numeric pads for entering numeric and arithmetic data, and a switch for turning the computer on and off. Some keyboards, including most for laptop computers, also incorporate a trackball, mouse pad, or other cursor-directing device. No standard exists for positioning the function, numeric, and other buttons on a keyboard relative to the QWERTY and other typewriting keys. Thus layouts vary on keyboards.

In the 1930s, American educators August Dvorak and William Dearly designed this key set so that the letters th


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