Monday, April 19, 2010

computer history

Part I

Webster's Dictionary defines "computer" as any programmable electronic device that can store, retrieve, and process data. The basic idea of computing develops in the 1200's when a Moslem cleric proposes solving problems with a series of written procedures.

As early as the 1640's mechanical calculators are manufactured for sale. Records exist of earlier machines, but Blaise Pascal invents the first commercial calculator, a hand powered adding machine. Although attempts to multiply mechanically were made by Gottfried Liebnitz in the 1670s the first true multiplying calculator appears in Germany shortly before the American Revolution.

In 1801 a Frenchman, Joseph-Marie Jacquard builds a loom that weaves by reading punched holes stored on small sheets of hardwood. These plates are then inserted into the loom which reads (retrieves) the pattern and creates(process) the weave. Powered by water, this "machine" came 140 years before the development of the modern computer.

Ada Countess Lovelace
Ada Lovelace

Shortly after the first mass-produced calculator(1820), Charles Babbage begins his lifelong quest for a programmable machine. Although Babbage was a poor communicator and record-keeper, his difference engine is sufficiently developed by 1842 that Ada Lovelace uses it to mechanically translate a short written work. She is generally regarded as the first programmer. Twelve years later George Boole, while professor of Mathematics at Cork University, writes An Investigation of the Laws of Thought(1854), and is generally recognized as the father of computer science.

The 1890 census is tabulated on punch cards similar to the ones used 90 years earlier to create weaves. Developed by Herman Hollerith of MIT, the system uses electric power(non-mechanical). The Hollerith Tabulating Company is a forerunner of today's IBM.

Just prior to the introduction of Hollerith's machine the first printing calculator is introduced. In 1892 William Burroughs, a sickly ex-teller, introduces a commercially successful printing calculator. Although hand-powered, Burroughs quickly introduces an electronic model.

In 1925, unaware of the work of Charles Babbage, Vannevar Bush of MIT builds a machine he calls the differential analyzer. Using a set of gears and shafts, much like Babbage, the machine can handle simple calculus problems, but accuracy is a problem.

The period from 1935 through 1952 gets murky with claims and counterclaims of who invents what and when. Part of the problem lies in the international situation that makes much of the research secret. Other problems include poor record-keeping, deception and lack of definition.

In 1935, Konrad Zuse, a German construction engineer, builds a mechanical calculator to handle the math involved in his profession. Shortly after completion, Zuse starts on a programmable electronic device which he completes in 1938.

John Vincent Atanasoff
Courtesy Jo Campbell
The Shore Journal

John Vincent Atanasoff begins work on a digital computer in 1936 in the basement of the Physics building on the campus of Iowa State. A graduate student, Clifford (John) Berry assists. The "ABC" is designed to solve linear equations common in physics. It displays some early features of later computers including electronic calculations. He shows it to others in 1939 and leaves the patent application with attorneys for the school when he leaves for a job in Washington during World War II. Unimpressed, the school never files and ABC is cannibalized by students.

The Enigma
Courtesy U. S. Army

The Enigma, a complex mechanical encoder is used by the Germans and they believe it to be unbreakable. Several people involved, most notably Alan Turing, conceive machines to handle the problem, but none are technically feasible. Turing proposes a "Universal Machine" capable of "computing" any algorithm in 1937. That same year George Steblitz creates his Model K(itchen), a conglomeration of otherwise useless and leftover material, to solve complex calculations. He improves the design while working at Bell Labs and on September 11, 1940, Steblitz uses a teletype machine at Dartmouth College in New Hampshire to transmit a problem to his Complex Number Calculator in New York and receives the results. It is the first example of a network.

First in Poland, and later in Great Britain and the United States, the Enigma code is broken. Information gained by this shortens the war. To break the code, the British, led by Touring, build the Colossus Mark I. The existence of this machine is a closely guarded secret of the British Government until 1970. The United States Navy, aided to some extent by the British, builds a machine capable of breaking not only the German code but the Japanese code as well.
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how fast you in computer science

Computer technology keeps advancing at an amazing pace. Today's home computers have more memory, run faster and are relatively less expensive than computers from ten or even five years ago. Is there a way to measure how fast your computer is? You might think that you could tell simply from the processor clock frequency, but this doesn't tell the whole story. The clock frequency just tells how many operations per second the CPU can perform. In modern multi-tasking operating systems, the CPU's time is split between many programs running at once. Also, the central processor (CPU) sends data to and receives data from other subsystems on the computer (e.g., memory, disk drives, video display) which usually run at slower speeds. Modern processors are equipped with high-speed data buffers (called caches) to alleviate these bottlenecks. There are also many strategies for optimizing the order of operations in a program for greatest efficiency.

In this project you will use a Java applet (see Experimental Procedure, below) to measure how long it takes for the computer to perform arithmetic operations (addition, subtraction, multiplication and division) with various data types (integers, long integers, floating point numbers and double-precision floating point numbers).

Measuring how long an operation takes provides useful information, both for optimizing algorithm performance, and also as a "benchmark" comparison between two computers. However, you must keep in mind that with today's multi-tasking operating systems, measuring the execution time of any single process is difficult. The operating system splits CPU time between all of the programs that are running. No program has "exclusive" access to the CPU. Generally, CPU processing speed is fast enough so that you don't notice this because programs appear to be instantly responsive. Behind the scenes though, each program is getting a slice of CPU time, then waiting for its next turn before it can run again.

So it is important to remember that, due to multi-tasking, the processing times you measure with the applet below will not represent the actual CPU time required to perform an addition or subtraction. In order for the applet to give you a best estimate, keep the number of open applications to a minimum, and make sure that any open applications are not performing tasks that require lots of CPU time (e.g., printing files or downloading content from the Internet).
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output device

Computer Output Devices

Computer Output Devices

Output Device
Output hardware consists of external devices that transfer information from the computer's CPU to the computer user. A video display, or screen, converts information generated by the computer into visual information.

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Displays commonly take one of two forms: a video screen with a cathode ray tube (CRT) or a video screen with a liquid crystal display (LCD).

A CRT-based screen, or monitor, looks similar to a television set. Information from the CPU is displayed using a beam of electrons that scans a phosphorescent surface that emits light and creates images.

Flat Panel or LCD
An LCD-based screen displays visual information on a flatter and smaller screen than a CRT-based video monitor. LCDs are frequently used in laptop computers.

Printers take text and image from a computer and print them on paper. Dot-matrix printers use tiny wires to impact upon an inked ribbon to form characters. Laser printers employ beams of light to draw images on a drum that then picks up fine black particles called toner. The toner is fused to a page to produce an image. Inkjet printers fire droplets of ink onto a page to form characters and pictures.

Ahh... Gamers can not ignore this category. However, we'll talk about that in later time.

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mother board

What is Motherboard?

Computer Parts - Mother Board

A motherboard is also known as a main board, system board and logic board. A common abbreviation is ‘mobo'. They can be found in a variety of electrical devices, ranging from a TV to a computer.

Generally, they will be referred to as a motherboard or a main board when associated with a complex device such as a computer, which is what we shall look at. Put simply, it is the central circuit board of your computer.

All other components and peripherals plug into it, and the job of the motherboard is to relay information between them all. Despite the fact that a better motherboard will not add to the speed of your PC, it is none-the-less important to have one that is both stable and reliable, as its role is vital.

A motherboard houses the BIOS (Basic Input/Output System), which is the simple software run by a computer when initially turned on. Other components attach directly to it, such as the memory, CPU (Central Processing Unit), graphics card, sound card, hard-drive, disk drives, along with various external ports and peripherals.

There are a lot of motherboards on the market to choose from. The big question is how do you go about choosing which one is right for you? Different motherboards support different components, and so it is vital you make a number of decisions concerning general system specifications before you can pick the right motherboard.

A motherboard can come in many configurations to fit different needs and budgets. At its most basic, it comes with several interfaces for necessary components and a BIOS chip set to control setup of the motherboard. Many computer enthusiasts favor one type of BIOS over another and will choose a motherboard partially based on the BIOS manufacturer.

An equally important feature of the motherboard is the type of CPU it will support. Some motherboards support AMD CPUs, while others support Intel processors. If you purchase your case before other components, the first factor to think about motherboard is the size, or form factor. A form factor is a standardized motherboard size.

If you think about fitting a motherboard in a case, there are numbers of mounting holes, slot locations and PSU connectors. The most popular motherboard form factor today is ATX, which evolved from it's predecessor, the Baby AT, a smaller version of the AT (Advanced Technology) form factor. Generally todays computers have ATX form factor motherboard.


Chipsets are a crucial part of a motherboard - they control the system and its’ capabilities. Furthermore, a chipset supports the facilities offered by the processor. A chipset is part of the motherboard, and cannot be upgraded without upgrading the whole board. It is therefore important to make sure you choose the right one for you in the first place.

There are a few main producers of chipsets, which are AMD, Intel, NVidia and Via: The latter two make chipsets for both AMD and Intel processors; AMD and Intel only make chipsets compatible with their own processors.

Another important consideration is the amount and type of RAM the motherboard will support. It is always best to buy a board that supports more RAM than currently needed. If new technology for RAM chips are available, getting a board that supports the newer chips will help future-proof the investment.

The number of PCI slots varies from motherboard to motherboard, as do other interfaces like the number of SATA ports, different RAID abilities, and USB and Firewire ports. As mentioned earlier, sound and video capability might be built-in, although enthusiasts generally prefer to disable internal video, sound and add superior third party cards.

Computer display is an important issue as there are many kinds of graphics cards available these days. Graphics cards vary from PCI or AGP. These days, PCI is ruling the market but one will find that AGP graphics cards are still in use.

One of the best things you can do when looking for a motherboard is to read lots of reviews. They will give you good information about how the board performs and what it is compatible with. Never make a judgement on one review alone and wherever possible ask for recommendations from other people.

Unless you have limitless resources, price is always a consideration when buying computer component. A motherboard usually takes up a fairly large part of any PC budget, so it requires careful consideration. It is worth bearing in mind that cheaper boards sometimes support only more expensive components. If this is the case, work out the total cost of buying the board and components as sometimes it may be worth spending a little more on a more expensive board. A cheap motherboard may be unreliable and more trouble than it is worth. A motherboard is one of those components where it pays to spend a little extra.

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computer input device

Computer Input Device

Computer Input Devices
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Computer Input Devices
Input devices consists of external devices - that is, devices outside of the computer's CPU - that provide information and instructions to the computer.

Light pen
A light pen is a stylus with a light sensitive tip that is used to draw directly on a computer's video screen or to select information on the screen by pressing a clip in the light pen or by pressing the light pen against the surface of the screen. The pen contains light sensors that identify which portion of the screen it is passed over.

A mouse is a pointing device designed to be gripped by one hand. It has a detection device (usually a ball) on the bottom that enables the user to control the motion of an on-screen pointer, or cursor, by moving the mouse on a flat surface. As the device moves across the surface, the cursor moves across the screen. To select items or choose commands on the screen, the user presses a button on the mouse.

A joystick is a pointing device composed of a lever that moves in multiple directions to navigate a cursor or other graphical object on a computer screen.

A keyboard is a typewriter-like device that allows the user to type in text and commands to the computer. Some keyboards have special function keys or integrated pointing devices, such as a trackball or touch-sensitive regions that let the user's finger motions move an on-screen cursor.


Optical Scanner
An optical scanner uses light-sensing equipment to convert images such as a picture or text into electronic signals that can be manipulated by a computer. For example, a photograph can be scanned into a computer and then included in a text document created on that computer.

The two most common scanner types are the flatbed scanner, which is similar to an office photocopier, and the handheld scanner, which is passed manually across the image to be processed.

A microphone is a device for converting sound into signals that can then be stored, manipulated, and played back by the computer.

voice recognition
A voice recognition module is a device that converts spoken words into information that the computer can recognize and process.

A modem, which stands for modulator-demodulator, is a device that connects a computer to a telephone line or cable television network and allows information to be transmitted to or received from another computer. Each computer that sends or receives information must be connected to a modem. The digital signal sent from one computer is converted by the modem into an analog signal, which is then transmitted by telephone lines or television cables to the receiving modem, which converts the signal back into a digital signal that the receiving computer can understand.

There are few different types of Modems including...
Analog: 56K (52K top speed) using telephone line.
DSL/ADSL: Top speed can reach as high as 5 Mb in residential using telephone line.
Cable: Top speed about 8 Mb using Cable.
FiberOptic: Can reach 30Mbps depend on your available provider.

Modem is input device as well as output device. So, we will place detaied articles about modems under "Networking" category.
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computer shortcuts

Accessibility Keyboard Shortcuts

1) Right SHIFT for eight seconds (Switch FilterKeys either on or off)

2) Left ALT+left SHIFT+PRINT SCREEN (Switch High Contrast either on or off)

3) Left ALT+left SHIFT+NUM LOCK (Switch the MouseKeys either on or off)

4) SHIFT five times (Switch the StickyKeys either on or off)

5) NUM LOCK for five seconds (Switch the ToggleKeys either on or off)
6) Windows Logo +U (Open Utility Manager)

Windows Explorer Keyboard Shortcuts

1) END (Display the bottom of the active window)
2) HOME (Display the top of the active window)
3) NUM LOCK+Asterisk sign (*) (Display all of the subfolders that are under the selected folder)
4) NUM LOCK+Plus sign (+) (Display the contents of the selected folder)
5) NUM LOCK+Minus sign (-) (Collapse the selected folder)
6) LEFT ARROW (Collapse the current selection if it is expanded, or select the parent folder)
7) RIGHT ARROW (Display the current selection if it is collapsed, or select the first subfolder)

Shortcut Keys for Character Map

After you double-click a character on the grid of characters, you can move through the grid by using the keyboard shortcuts:
1) RIGHT ARROW (Move to the right or to the beginning of the next line)
2) LEFT ARROW (Move to the left or to the end of the previous line)
3) UP ARROW (Move up one row)
4) DOWN ARROW (Move down one row)
5) PAGE UP (Move up one screen at a time)
6) PAGE DOWN (Move down one screen at a time)
7) HOME (Move to the beginning of the line)
8) END (Move to the end of the line)
9) CTRL+HOME (Move to the first character)
10) CTRL+END (Move to the last character)
11) SPACEBAR (Switch between Enlarged and Normal mode when a character is selected)

Microsoft Management Console (MMC) Main Window Keyboard Shortcuts

1) CTRL+O (Open a saved console)
2) CTRL+N (Open a new console)
3) CTRL+S (Save the open console)
4) CTRL+M (Add or remove a console item)
5) CTRL+W (Open a new window)
6) F5 key (Update the content of all console windows)
7) ALT+SPACEBAR (Display the MMC window menu)
8) ALT+F4 (Close the console)
9) ALT+A (Display the Action menu)
10) ALT+V (Display the View menu)
11) ALT+F (Display the File menu)
12) ALT+O (Display the Favorites menu)
13) MMC Console Window Keyboard Shortcuts
14) CTRL+P (Print the current page or active pane)
15) ALT+Minus sign (-) (Display the window menu for the active console window)
16) SHIFT+F10 (Display the Action shortcut menu for the selected item)
17) F1 key (Open the Help topic, if any, for the selected item)
18) F5 key (Update the content of all console windows)
19) CTRL+F10 (Maximize the active console window)
20) CTRL+F5 (Restore the active console window)
21) ALT+ENTER (Display the Properties dialog box, if any, for the selected item)
22) F2 key (Rename the selected item)
23) CTRL+F4 (Close the active console window. When a console has only one console window, this shortcut closes the console)

Remote Desktop Connection Navigation

1) CTRL+ALT+END (Open the m*cro$oft Windows NT Security dialog box)
2) ALT+PAGE UP (Switch between programs from left to right)
3) ALT+PAGE DOWN (Switch between programs from right to left)
4) ALT+INSERT (Cycle through the programs in most recently used order)
5) ALT+HOME (Display the Start menu)
6) CTRL+ALT+BREAK (Switch the client computer between a window and a full screen)
7) ALT+DELETE (Display the Windows menu)
8) CTRL+ALT+Minus sign (-) (Place a snapshot of the active window in the client on the Terminal server clipboard and provide the same functionality as pressing PRINT SCREEN on a local computer.)
9) CTRL+ALT+Plus sign (+) (Place a snapshot of the entire client window area on the Terminal server clipboard and provide the same functionality as pressing ALT+PRINT SCREEN on a local computer.)

Microsoft Internet Explorer Navigation

1) CTRL+B (Open the Organize Favorites dialog box)
2) CTRL+E (Open the Search bar)
3) CTRL+F (Start the Find utility)
4) CTRL+H (Open the History bar)
5) CTRL+I (Open the Favorites bar)
6) CTRL+L (Open the Open dialog box)
7) CTRL+N (Start another instance of the browser with the same Web address)
8) CTRL+O (Open the Open dialog box, the same as CTRL+L)
9) CTRL+P (Open the Print dialog box)
10) CTRL+R (Update the current Web page)
11) CTRL+W (Close the current window)
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data storage device

omputer Storage Devices

Computer Storage Devices

Storage Devices
Storage hardware provides permanent storage of information and programs for retrieval by the computer. The two main types of storage devices are disk drives and memory.

There are several types of disk drives: hard, floppy, magneto-optical, and compact.

Hard disk drive
Hard disk drives store information in magnetic particles embedded in a disk. Usually a permanent part of the computer, hard disk drives can store large amounts of information and retrieve that information very quickly.

Floppy disk drive
Floppy disk drives also store information in magnetic particles embedded in removable disks that may be floppy or rigid. Floppy disks store less information than a hard disk drive and retrieve the information at a much slower rate.

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Magneto-optical disc drive
Magneto-optical disc drives store information on removable discs that are sensitive to both laser light and magnetic fields. They can typically store as much information as hard disks, but they have slightly slower retrieval speeds.

Compact disc drive
Compact disc drives store information on pits burned into the surface of a disc of reflective material. CD-ROMs can store about as much information as a hard drive but have a slower rate of information retrieval. A digital video disc (DVD) looks and works like a CD-ROM but can store more than 7 times as much information.

Memory refers to the computer chips that store information for quick retrieval by the CPU. Random access memory RAM is used to store the information and instructions that operate the computer's programs.

Typically, programs are transferred from storage on a disk drive to RAM. RAM is also known as volatile memory because the information within the computer chips is lost when power to the computer is turned off.

Read-only memory (ROM) contains critical information and software that must be permanently available for computer operation, such as the operating system that directs the computer's actions from start up to shut down. ROM is called nonvolatile memory because the memory chips do not lose their information when power to the computer is turned off.

Some devices serve more than one purpose. For example, floppy disks may also be used as input devices if they contain information to be used and processed by the computer user. In addition, they can be used as output devices if the user wants to store the results of computations on them.
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