computer

computernetworking

A computer network is referred to as client/server if (at least) one of the computers is used to "serve" other computers referred to as "clients". Besides the computers, other types of devices can be part of the network:
In a client/server environment, each computer still holds (or can still hold) its (or some) resources and files. Other computers can also access the resources stored in a computer, as in a peer-to-peer scenario. One of the particularities of a client/server network is that the files and resources are centralized. This means that a computer, the server, can hold them and other computers can access them. Since the server is always On, the client machines can access the files and resources without caring whether a certain computer is On.
Another big advantage of a client/server network is that security is created, managed, and can highly get enforced. To access the network, a person, called a user must provide some credentials, including a username and a password. If the credentials are not valid, the user can be prevented from accessing the network.
The client/server type of network also provides many other advantages such as centralized backup, Intranet capability, Internet monitoring, etc.
In these series of lessons, the network we will build is based on Microsoft Windows operating systems (I have been able to fully connect some versions of Linux, such as Novell SUSE Linux, into a Microsoft Windows-based network but at the time of this writing, I will not be able to address that).
In our lessons, we will mention the names of companies or provide links. These are only indications and not advertisements. Any other company or link that provides the mentioned service is suitable.


:: Note
It may be a good idea to know a little bit about MS Windows before getting into networking.
:: Note
Don’t think that you can install a (commercial) software product in one computer and use it on many computers. It doesn’t work like that.


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hard disk drive

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.The commercial usage of hard disk drives began in 1956 with the shipment of an IBM 305 RAMAC system including IBM Model 350 disk storage.
For many years, hard disk drives were large, cumbersome devices, more suited to use in the protected environment of a data center or large office than in a harsh industrial environment (due to their delicacy), or small office or home (due to their size and power consumption). Before the early 1980s, most hard disk drives had 8-inch (actually, 210 - 195 mm) or 14-inch platters, required an equipment rack or a large amount of floor space (especially the large removable-media drives, which were frequently comparable in size to washing machines), and in many cases needed high-current and/or three-phase power hookups due to the large motors they used. Because of this, hard disk drives were not commonly used with microcomputers until after 1980, when Seagate Technology introduced the ST-506 the first 5.25-inch hard drives, with a formatted capacity of 5 megabytes.
The capacity of hard drives has grown exponentially over time. With early personal computers, a drive with a 20 megabyte capacity was considered large. During the mid to late 1990s, when PCs were capable of storing not just text files and documents but pictures, music, and video, internal drives were made with 8 to 20 GB capacities. As of early 2009, desktop hard disk drives typically have a capacity of 320 to 500 gigabytes, while the largest-capacity drives are 2 terabyt

Printing technology

Printers are routinely classified by the underlying print technology they employ; numerous such technologies have been developed over the years. The choice of print engine has a substantial effect on what jobs a printer is suitable for, as different technologies are capable of different levels of image/text quality, print speed, low cost, noise; in addition, some technologies are inappropriate for certain types of physical media (such as carbon paper or transparencies).
Another aspect of printer technology that is often forgotten is resistance to alteration: liquid ink such as from an inkjet head or fabric ribbon becomes absorbed by the paper fibers, so documents printed with a liquid ink sublimation printer are more difficult to alter than documents printed with toner or solid inks, which do not penetrate below the paper surface.
Checks should either be printed with liquid ink or on special "check paper with toner anchorage" For similar reasons carbon film ribbons for IBM Selectric typewriters bore labels warning against using them to type negotiable instruments such as checks. The machine-readable lower portion of a check, however, must be printed using MICR toner or ink. Banks and other clearing houses employ automation equipment that relies on the magnetic flux from these specially printed characters to function properly.

Printer

Printer is output Device which gives the output in user acceptable format (Ref:- by Prof Ramanand Chivate ) In computing, a printer is a peripheral which produces a hard copy (permanent readable text and/or graphics) of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most newer printers, a USB cable to a computer which serves as a document source. Some printers, commonly known as network printers, have built-in network interfaces (typically wireless and/or Ethernet), and can serve as a hardcopy device for any user on the network. Individual printers are often designed to support both local and network connected users at the same time. In addition, a few modern printers can directly interface to electronic media such as memory sticks or memory cards, or to image capture devices such as digital cameras, scanners; some printers are combined with a scanner and/or fax machine in a single unit, and can function as photocopiers. Printers that include non-printing features are sometimes called Multifunction printers (MFP), Multi-Function Devices (MFD), or All-In-One (AIO) printers. Most MFPs include printing, scanning, and copying among their features.
A Virtual printer is a piece of computer software whose user interface and API resemble that of a printer driver, but which is not connected with a physical computer printer.
Printers are designed for low-volume, short-turnaround print jobs; requiring virtually no setup time to achieve a hard copy of a given document. However, printers are generally slow devices (30 pages per minute is considered fast; and many inexpensive consumer printers are far slower than that), and the cost per page is actually relatively high. However this is offset by the on-demand convenience and project management costs being more controllable compared to an out-sourced solution. The printing press naturally remains the machine of choice for high-volume, professional publishing. However, as printers have improved in quality and performance, many jobs which used to be done by professional print shops are now done by users on local printers; see desktop publishing. The world's first computer printer was a 19th century mechanically driven apparatus invented by Charles Babbage for his Difference Engine.

word processor

A word processor (more formally known as document preparation system) is a computer application used for the production (including composition, editing, formatting, and possibly printing) of any sort of printable material.
Word processor may also refer to an obsolete type of stand-alone office machine, popular in the 1970s and 80s, combining the keyboard text-entry and printing functions of an electric typewriter with a dedicated computer for the editing of text. Although features and design varied between manufacturers and models, with new features added as technology advanced, word processors for several years usually featured a monochrome display and the ability to save documents on memory cards or diskettes. Later models introduced innovations such as spell-checking programs, increased formatting options, and dot-matrix printing. As the more versatile combination of a personal computer and separate printer became commonplace, the word processor as a stand-alone office machine disappeared.
Word processors are descended from early text formatting tools (sometimes called text justification tools, from their only real capability). Word processing was one of the earliest applications for the personal computer in office productivity.
Although early word processors used tag-based markup for document formatting, most modern word processors take advantage of a graphical user interface providing some form of What You See Is What You Get editing. Most are powerful systems consisting of one or more programs that can produce any arbitrary combination of images, graphics and text, the latter handled with type-setting capability.
Microsoft Word is the most widely used computer word processing system; Microsoft estimates over five hundred million people use the Office suite, which includes Word. There are also many other commercial word processing applications, such as WordPerfect, which dominated the market from the mid-1980s to early-1990s, particularly for machines running Microsoft's MS-DOS operating system. Open-source applications such as Abiword, KWord, LyX and OpenOffice.org Writer are rapidly gaining in popularity.[citation needed] Online word processors such as Google Docs are a relatively new category.

Text cursor

In most command line interfaces or text editors, the cursor is an underscore, a solid rectangle, or a vertical line, which may be flashing or steady, indicating where text will be placed when entered (the insertion point). In the old days of text mode displays, it was not possible to show a vertical bar between characters to show where the new text would be inserted, so an underscore or block cursor was used instead. In situations where a block was used the block was usually created by inverting the pixels of the character using the boolean math exclusive or function. On text editors and word processors of modern design on bitmapped displays, the vertical bar is typically used instead. Some older graphical user interfaces such as OPEN LOOK used a caret-shaped insertion marker.[citation needed] Still today, the text cursor is sometimes called caret. Some details of the vertical bar's origins have been described in Bill Moggridge's Designing Interactions (ISBN 0262134748).

Cursor (computers)

In computing, a cursor is an indicator used to show the position on a computer monitor or other display device that will respond to input from a text input or pointing device. The text cursor may be referred to as a caret in some cases. This term came about from older Unix systems that used the caret symbol as a text insertion indicator[citation needed]. The mouse cursor may be referred to as a mouse pointer, owing to its arrow shape on some systems.

pointing device(Mouse)

A pointing device is any human interface device that allows a user to input spatial data to a computer. In the case of mice and touch screens, this is usually achieved by detecting movement across a physical surface. Analog devices, such as 3D mice, joysticks, or pointing sticks, function by reporting their angle of deflection. Movements of the pointing device are echoed on the screen by movements of the cursor, creating a simple, intuitive way to navigate a computer's graphical user interface (GUI).

Computer keyboard

In computing, a keyboard is an input device, partially modeled after the typewriter keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches. A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or computer commands.
In normal usage, the keyboard is used to type text and numbers into a word processor, text editor or other program. In a modern computer, the interpretation of keypresses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all keypresses to the controlling software. Keyboards are also used for computer gaming, either with regular keyboards or by using keyboards with special gaming features, which can expedite frequently used keystroke combinations. A keyboard is also used to give commands to the operating system of a computer, such as Windows' Control-Alt-Delete combination, which brings up a task window or shuts down the machine.

monitor

A monitor or display (sometimes called a visual display unit) is a piece of electrical equipment which displays images generated by devices such as computers, without producing a permanent record. The monitor comprises the display device, circuitry, and an enclosure. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD), while older monitors use a cathode ray tube (CRT).

Pentium 4 computer

The Pentium 4 brand refers to Intel's line of single-core mainstream and high-end desktop and laptop central processing units (CPUs) introduced on November 20, 2000(August 8, 2008 was the date of last shipments of Pentium 4s). They had the 7th-generation microarchitecture, called NetBurst, which was the company's first all-new design since 1995, when the Intel P6 microarchitecture of the Pentium Pro CPUs had been introduced. NetBurst differed from the preceding Intel P6 (Pentium III, II, etc.) by featuring a very deep instruction pipeline to achieve very high clock speeds(up to 3.8 GHz) limited only by TDPs reaching up to 115 W in 3.4 GHz –3.8 GHz Prescott and Prescotts 2M cores (a high TDP requires additional cooling that can be noisy or expensive). In 2004, the initial 32-bit x86 instruction set of the Pentium 4 microprocessors was extended by the 64-bit x86-64 set.
The first Pentium 4 cores, codenamed Willamette, were clocked from 1.3 GHz to 2 GHz and the first Willamette processor was released on November 20, 2000 using Socket 423. Notable with the introduction of the Pentium 4 was the 400 MHz FSB. It actually operated at 100 MHz but the FSB was quad-pumped, meaning that the maximum transfer rate was four times that of a normal bus, so it was considered to run at 400 MHz. The AMD Athlon's double-pumped FSB was running at 200 MHz or 266 MHz at that time.
Pentium 4 CPUs introduced the SSE2 and, in the Prescott-based Pentium 4s, SSE3 instruction sets to accelerate calculations, transactions, media processing, 3D graphics, and games. Later versions featured Hyper-Threading Technology (HTT), a feature to make one physical CPU work as two logical and virtual CPUs. Intel also marketed a version of their low-end Celeron processors based on the NetBurst microarchitecture (often referred to as Celeron 4), and a high-end derivative, Xeon, intended for multiprocessor servers and workstations. In 2005, the Pentium 4 was complemented by the Pentium D and Pentium Extreme Edition dual-core CPUs.

Random-access memory

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 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 a type of flash memory called NOR-Flash.

DVD Audio

DVD Audio is a format for delivering high fidelity audio content on a DVD. It offers many channel configuration options (from mono to 5.1 surround sound) at various sampling frequencies (up to 24-bits/192 kHz versus CDDA's 16-bits/44.1 kHz). Compared with the CD format, the much higher-capacity DVD format enables the inclusion of considerably more music (with respect to total running time and quantity of songs) and/or far higher audio quality (reflected by higher sampling rates and greater sample resolution, and/or additional channels for spatial sound reproduction).
Despite DVD Audio's superior technical specifications, there is debate as to whether the resulting audio enhancements are distinguishable in typical listening environments. DVD Audio currently forms a niche market, probably due to the very sort of format war with rival standard SACD that DVD Video avoided

DVD Video

DVD Video is a standard for content on DVD media. In the U.S., mass retailer sales of DVD Video titles and players began in August 1997.By June 2003, weekly DVD Video rentals began outnumbering weekly VHS cassette rentals, reflecting the rapid adoption rate of the technology in the U.S. marketplace.Currently, DVD Video is the dominant form of home video distribution worldwide.
Although many resolutions and formats are supported, most consumer DVD Video discs use either 4:3 or anamorphic 16:9 aspect ratio MPEG-2 video, stored at a resolution of 720/704×480 (NTSC) or 720/704×576 (PAL) at 29.97, 25, or 23.976 FPS. Audio is commonly stored using the Dolby Digital (AC-3) or Digital Theater System (DTS) formats, ranging from 16-bits/48 kHz to 24-bits/96 kHz format with monaural to 6.1-channel "Surround Sound" presentation, and/or MPEG-1 Layer 2 and/or LPCM Stereophonic. Although the specifications for video and audio requirements vary by global region and television system, many DVD players support all possible formats. DVD Video also supports features such as menus, selectable subtitles, multiple camera angles, and multiple audio tracks.

Digital Versatile Disc or Digital Video Disc

DVD, also known as Digital Versatile Disc or Digital Video Disc, is an optical disc storage media format, and was invented in 1995. Its main uses are video and data storage. DVDs are of the same dimensions as compact discs (CDs), but store more than six times as much data.
Variations of the term DVD often describe the way data is stored on the discs: DVD-ROM (read only memory) has data that can only be read and not written; DVD-R and DVD+R (recordable) can record data only once, and then function as a DVD-ROM; DVD-RW (re-writable), DVD+RW, and DVD-RAM andom access memory) can all record and erase data multiple times. The wavelength used by standard DVD lasers is 650 nm; thus, the light has a red color.
DVD-Video and DVD-Audio discs refer to properly formatted and structured video and audio content, respectively. Other types of DVDs, including those with video content, may be referred to as DVD Data discs.

School abacus

School abacus used in Danish elementary school. Early 20th century.
Around the world, abaci have been used in pre-schools and elementary schools as an aid in teaching the numeral system and arithmetic.
In Western countries, a bead frame similar to the Russian abacus but with straight wires and a vertical frame has been common (see image). It is still often seen as a plastic or wooden toy.
The type of abacus shown here is often used to represent numbers without the use of place value. Each bead and each wire has the same value and used in this way it can represent numbers up to 100.

Roman abacus

The normal method of calculation in ancient Rome, as in Greece, was by moving counters on a smooth table. Originally pebbles, calculi, were used. Later, and in medieval Europe, jetons were manufactured. Marked lines indicated units, fives, tens etc. as in the Roman numeral system. This system of 'counter casting' continued into the late Roman empire and in medieval Europe, and persisted in limited use into the nineteenth century.
Writing in the 1st century BC, Horace refers to the wax abacus, a board covered with a thin layer of black wax on which columns and figures were inscribed using a stylus.
One example of archaeological evidence of the Roman abacus, shown here in reconstruction, dates to the 1st century AD. It has eight long grooves containing up to five beads in each and eight shorter grooves having either one or no beads in each. The groove marked I indicates units, X tens, and so on up to millions. The beads in the shorter grooves denote fives – five units, five tens etc., essentially in a bi-quinary coded decimal system, obviously related to the Roman numerals. The short grooves on the right may have been used for marking Roman ounces.