Data Between Computers On Disk Storage example essay topic

1. World War II is not generally remembered for triumphs of technology; however, it was during the war that computers were first created for a specific purpose. The British built a computer called Colossus to break the codes produced by the German Enigma encrypting machine. The Americans built the Electronic Numerical Integrator Analyzer and Computer (ENIAC) to produce missile trajectory tables. Reportedly, the Germans created a computer that was not limited to a specific task, but it was lost or destroyed in the war. These computers were by no means small or affordable; ENIAC cost $500,000 and weighed 30 tons.

2. The first computer that was affordable and could realistically be called a PC was the Altair 8800. It was produced in 1975 and had no keyboard. Programs and data were entered by flicking switches with results read by interpreting a pattern of small red lights.

It didn't take long for enthusiastic computer amateurs to find ways of expanding the Altair with a keyboard, video display, and diskette storage. Two enthusiasts, Stephen Jobs and Steve Wozniak, created a PC that came complete with display, built-in-keyboard and disk storage. They called it the Apple, and it was the first PC powerful and friendly enough to be more than a toy. 3.

The development that unleashed computers on society was not a technical invention. International Business Machines (IBM) made a marketing decision when creating their first PC, to keep the price down, they built the computer from components that were available off the shelf. They also made the overall design freely available to competitors. The only part of the machine IBM copyrighted was the Basic Input / Output System (BIOS). IBM's openness encouraged the creation of IBM clones that could use the same software and hardware add-ons.

In turn, the clones, while competing with IBM, at the same time helped establish the IBM architecture as the machine that software and add-on hardware developers would design for. The desktop PC that I use at work is a direct descendant of these machines. The PC's Role 4. My work PC enables me to research and compile technical reports, prepare presentations, produce formal letters / meeting agendas / minutes, manage my time / budgets /equipment inventories, communicate remotely and store or retrieve data. To help me complete these tasks, there are various software application programs loaded onto the computer. These programs run on an operating system, in this case Microsoft Windows NT, and are part of the Microsoft Office 2000 Professional suite.

They comprise: i. Word - a word processing program with the additional features of automatic formatting, easy-to-create tables and the ability to create and position graphics. ii. Excel - a spreadsheet program that enables the user to manage, format, chart and analyse data in cells and rows.. Powerpoint - a complete presentation graphics package, which enables the creation of fully formatted presentations or slides. iv. Access - a relational database construction program that allows the user to store, organise and easily retrieve information. vs. Outlook - electronic mail send / receive program, including a time management facility. vi. Explorer - intranet / internet navigation program.

There are also many other programs loaded onto the system for specific use, for example: RAF Report Writer, which is a package designed for the compilation of staff annual reports. 5. The specification of computer I am provided with for this purpose briefly consists of: i. 17" colour Super Video Graphics Array (SVGA) monitor. ii. Keyboard.. Mouse. iv.

Desktop System Unit containing a Pentium II Central Processing Unit (CPU), 7.81 gigabyte hard drive, 3.5" floppy disk drive and compact disk read / write drive. vs. Connected, through a local area network (LAN), to several types of printer. Networks 6. PCs serve only one user, so to enhance the amount of information available and retain a corporate standard computers can be linked together by a process known as networking. There are two main types of network: i. Wide area network (WAN), which can link a large number of machines together over a large area, by means of telephone lines. ii. Local area network (LAN), which is the type my PC is on, links a few machines by means of special wiring.

7. The main components of a LAN are: i. Workstation PCs. ii. A file saver, which is a high performance computer with increased hard disk storage capability.. Connecting cables. iv. A network operating system. vs. Interface cards, which plug into the workstation computers and connect them to the network cabling.

8. Two types of LAN network are available, star networks and ring networks. A star network has a main file server, and a number of terminals connected to it. In this system none of the terminals have their own hard disks, but access the main one in the server unit.

In ring networks each terminal has software loaded onto its own hard disk, and its own floppy disk drive for storing and retrieving data. They are connected to all other terminals in the network, and can communicate with any one of them. Although this system can sometimes be slow if under a heavy workload it has the advantages of being highly flexible and relatively cheap to install. Figure 1 shows a schematic of a ring network. Figure 1: A typical local area network Inside a PC 9. I will now describe the operation, purpose and interaction of the components in a basic PC, as depicted in Figure 2. i.

Monitor - A visual display unit creates an image out of coloured dots. The colours used are red, green and blue. To create an image, digital signals are sent from the operating environment or application software through a circuit called a digital-to-analog converter (DAC). The DAC compares the digital values to a table that contains the matching voltage levels for the three primary colours needed to create a single picture element (pixel).

A VGA adaptor then sends signals to 3 electron guns at the rear of the monitor's cathode ray tube (CRT). Through the vacuum inside the CRT, each electron gun shoots out a stream of electrons, one for each of the primary colours, the intensity of each stream controlled by the adaptor. The adaptor also sends signals to a mechanism called a magnetic deflection yoke (MDY) that focuses and aims the beams. This determines the monitor's resolution (the number of pixels displayed horizontally and vertically) and the refresh rate (how frequently the image is redrawn). The beams then pass through holes in a metal plate which keeps the beams precisely aligned with their targets on the inside of the CRT's screen. The electrons strike the phosphors coating the inside of the screen and the phosphors glow.

Three different phosphor materials are used (again one each for red, blue and green), and to create different colours the intensity of the electron beams is varied. After a beam leaves a phosphor dot, the phosphor glows briefly. For an image to remain stable, the phosphors must be reactivated by repeated scans of electron beams before the image fades away. The beams make one horizontal sweep across the screen and are then turned off; the MDY refocuses the beams back to a point just below the previous scan line before sweeping again. The MDY continually changes the angles at which the electron beams are bent so that they sweep across the entire screen from the upper left corner to the lower right.

A complete sweep of the screen is called a field. On completion of a field the process starts again. The screen is redrawn, or refreshed, about 60 times a second. ii. Mouse - The mouse is a pointing device.

A mechanical movement of the ball and roller mechanism within the mouse is translated into electrical signals that are then translated by the operating system into the movement of a pointer on the monitor's screen. How many times you click the buttons on top of the mouse and the position of the on-screen pointer, determines the task the software will perform.. Keyboard - The keyboard is the direct interface between the user and the PC. By pressing a key, there is a change in the current flow associated for that key. A microprocessor built into the keyboard constantly scans the circuits leading to the keys. By detecting both increases and decreases in current associated with keys, the processor can tell when a key has been pressed and subsequently released and scans all the keys hundreds of times a second.

Depending on which key is pressed, the processor generates a scan code and stores it in the keyboard's own memory buffer. The processor then sends a signal to the computer's Basic Input / Output System (BIOS) to tell the CPU that there is a scan code waiting for it. The BIOS reads the scan code and sends a signal to the keyboard to let it know that the code can now be deleted from the buffer. If the scan code is for a shift key or toggle key, such as Ctrl, Num Lock etc, the BIOS changes two bytes in a special area of memory to maintain a record of which of these keys has been pressed. For all other keys, the BIOS checks those two bytes to determine the status of the shift and toggle keys before translating the scan code into an ASCll code. The ASCll code is then stored in the computer's RAM memory buffer, where the operating system or application software retrieves it as soon as any current operation has finished. iv.

Connection interface - Many of the PC's internal components send or receive information from outside the casing. To simplify connecting external components to the internal ones, there is a selection of different types of connectors on the rear of a PC base unit. Each connector is different to prevent the inadvertent mis connection of components. vs. Power unit - All electricity enters the PC through a shielded metal box. Inside it, a transformer converts the current that comes from the mains into the voltages and current flows needed by various parts of the computer. vi. Fan - A fan provides cooling for the heat-critical components inside the case. The case is vented to allow a through-flow of air. vii.

Motherboard - Most of the components inside a PC are mounted on printed circuit boards. The motherboard is the largest printed circuit and acts as a junction box for power and data transfer between the other components. Expansion cards, the Central Processing Unit (CPU) and memory chips plug into the motherboard along with other circuit boards and disk drives. vs. CPU - This is the brain of the PC and is a tight, complex collection of microscopic transistors arranged so that they can manipulate data. The CPU handles most operations of the computer. Transistors are electrical switches in which off and on represent 0 and 1 in the binary system. To a computer, everything, mathematics, words, and software instructions are defined as a combination of binary numbers.

The brain within the brain of a Pentium II processor is called the Arithmetical Logic Unit (ALU), of which it has two. The ALU juggles all the data coming in the form of different combinations of 0's and 1's before sending it to a memory buffer for the software to retrieve. ix. Heat sink - Because processors produce so much heat, a heat sink is used to dissipate it, so that internal components don't melt. Heat sinks comprise a block of high heat conductivity material, usually metal alloy adjacent to the high heat producing component. They are manufactured with fins to give a large surface area for the dissipation of the heat. x. BIOS - If the CPU is the brain, then BIOS is the heart of the PC.

It comprises one or two chips that define the personality of the machine. The Basic Input / Output System knows the details of how the PC was put together and serves as an intermediary between the operating software running the computer and the various hardware components. This information is permanent and not affected by turning the PC's power off, known as non-volatile memory. xi. RAM - Random Access Memory chips are like a clear desktop to the PC.

Before it can do anything useful, it must move programs from disk storage to RAM. The data contained in documents, spreadsheets, graphics etc, must also be stored in RAM, if only momentarily, before the software can use the CPU to manipulate the data. When the PC is turned off, anything stored in RAM disappears, ready to be a clear desktop next time the PC is turned on. This is known as volatile memory and is contained in chips that plug into a connector on the motherboard called Single In-line Memory Module (SIMM) or Dual In-line Memory Module (DIMM). xii. CMOS + CMOS Battery - Complementary Metal Oxide Semiconductor is a special type of memory chip that uses a small lithium battery to retain information about the PC's hardware configuration even when the computer is turned off. It requires only about one-millionth of an amp to store the startup configuration of a PC for many years. x.

RTC - A battery powered Real Time Clock tracks the time even when the computer is turned off. Every second, the clock updates itself and stores the data in a buffer. When the PC is turned on, the BIOS checks with the RTC to get the current date and time and stores the information in the computer's system clock, which is in the CMOS. When a software program needs to know the date or time, it reads it from the CMOS system clock. xiv.

Sound card - This circuit board contains all the circuitry for recording and reproducing sound. It may be an expansion card or come built into a few chips on the motherboard. It can be attached, through the connection interface, to speakers, headphones, microphone or CD player input. xv. IDE controllers - Integrated Drive Electronics Controllers were developed to replace the disk controller card and the CMOS-based knowledge of every possible drive's physical geometry. These are usually built into the motherboard and provide connection slots for 40 wire ribbon cables that send signals controlling the floppy, hard and CD read / write drives and also provide a medium for the transfer of data, known as data busses. xvi. Hard drive - This is the main memory storage and a permanent fixture within the PC.

It comprises magnetic recordings on hard, thin platters that spin at very high speed. It contains the system files that initiate mechanical life in the computer and also the programs and documents. Before anything can be stored on a magnetic disk, the disk must be formatted. Formatting creates a 'roadmap' that allows the drive to store and retrieve data in an orderly manner.

This 'roadmap' consists of magnetic markers embedded in the magnetic film on the surface of the disk. The markers divide the disks up into sectors, like a pie slice, and tracks, concentric circles. These divisions organise the disk so that data can be recorded or accessed quickly by the read / write heads that move back and forth over the disks as they spin. To record binary numbers onto a magnetic disk, the read write head magnetizes iron particles in the disk coating to align them in two bands. If the number is to represent 0, the bands are aligned with magnetic poles facing in the same direction. For a 1, each band's magnetized poles are in opposite directions.

Together, the two bands represent the smallest unit of data a computer can handle, known as a 'bit'. The hard drive stores data on a microscopic scale and within fractions of a second. To achieve this, the read / write heads are within five hundred thousands of an inch of the disk surface. The memory is non-volatile, as when the power is turned off, the data is still there. xvii. Floppy disk drive - The drive takes a 3.5" floppy disk made of mylar, coated either side with a magnetic material that can hold 1.44 megabytes of data, which is equivalent to 500 pages of typed, unformatted, double-spaced text. Data can be written onto, or read from disks.

These disks are removable, providing a convenient way of transferring data between computers. xv. CD read / write drive - Similar to the floppy disk drive in that it is a means of transferring data between computers on disk storage. Compact Disks hold up to 650 megabytes of data and are made of a clear polycarbonate disk sandwiching a thin film of metal. To write onto the disk, a laser beam selectively heats areas to melt the metal crystals, changing them to a non-crystalline phase, which reflects less light than the unchanged area around them.

This leaves a spiral made up of reflective and non-reflective segments representing 0's and 1's that can be read by the 'read laser'. xix. Modem - This connects the PC to a telephone line so that data may be downloaded or sent from / to remote computers. Modems also come as external devices. Figure 2: Basic PC Layout.