Basic Computer Elements

Basic Computer Elements

Basic Computer Elements:  In generally used computers one can find that there are four basic computer elements following are the elements.
(1) ALU (Arithmetic Logic Unit): The ALU is the digital circuit that is able to perform different types of functions, such as Addition, Subtraction, and Multiplication etc.
(2) Control Unit: The control unit is the part of CPU (central processing unit) or other devices that performs the duty to direct its operations, the control unit is just like a finite state machine that has some finite states and the transaction from one state to the other state is called action.

(3) Memory: The memory is another very important element of the computer without memory the computer can't operate in today's modern age it is called the RAM (Random Access Memory) when ever we give some instruction to the computer it passes through RAM to the Processor and the processor processes it and send it back. The main reason behind memory is that it is faster in communication with the processor then the other memory devices such as hard disk etc.

(4) Input/output  devices: The input and output devices is another important element for example the processor is the input device and it gives its output to the monitor etc for output.
There is another very important point the basic elements are considered as CPU (central Processing Unit), I/O devices, and Memory actually the CPU is the composition of different other elements such as ALU, Control Unit, Registers which is another type of memory

Unit 1

1.  A computer is a device that accepts information (in the form of digitalized data) and manipulates it for some result based on a program or sequence of instructions on how the data is to be processed. Complex computers also include the means for storing data (including the program, which is also a form of data) for some necessary duration. A program may be invariable and built into the computer (and called logic circuitry as it is on microprocessors) or different programs may be provided to the computer (loaded into its storage and then started by an administrator or user). Today's computers have both kinds of programming.

Most histories of the modern computer begin with the Analytical Engine envisioned by Charles Babbage following the mathematical ideas of George Boole, the mathematician who first stated the principles of logic inherent in today's digital computer. Babbage's assistant and collaborator, Ada Lovelace, is said to have introduced the ideas of program loops and subroutines and is sometimes considered the first programmer. Apart from mechanical calculators, the first really useable computers began with the vacuum tube, accelerated with the invention of the transistor, which then became embedded in large numbers in integrated circuits, ultimately making possible the relatively low-cost personal computer.

2. The history of computer development is often referred to in reference to the different generations of computing devices. Each generation of computer is characterized by a major technological development that fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper, more powerful and more efficient and reliable devices.

Read about each generation and the developments that led to the current devices that we use today.

First Generation (1940-1956) Vacuum Tubes
The first computers used vacuum tubes for circuitry and magnetic drums for memory, and were often enormous, taking up entire rooms. They were very expensive to operate and in addition to using a great deal of electricity, generated a lot of heat, which was often the cause of malfunctions.
First generation computers relied on machine language, the lowest-level programming language understood by computers, to perform operations, and they could only solve one problem at a time. Input was based on punched cards and paper tape, and output was displayed on printouts.
The UNIVAC and ENIAC computers are examples of first-generation computing devices. The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951.
Second Generation (1956-1963) Transistors
Transistors replaced vacuum tubes and ushered in the second generation of computers. The transistor was invented in 1947 but did not see widespread use in computers until the late 1950s. The transistor was far superior to the vacuum tube, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their first-generation predecessors. Though the transistor still generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube. Second-generation computers still relied on punched cards for input and printouts for output.

Second-generation computers moved from cryptic binary machine language to symbolic, or assembly, languages, which allowed programmers to specify instructions in words. High-level programming languages were also being developed at this time, such as early versions of COBOL and FORTRAN. These were also the first computers that stored their instructions in their memory, which moved from a magnetic drum to magnetic core technology.

The first computers of this generation were developed for the atomic energy industry.

Third Generation (1964-1971) Integrated Circuits
The development of the integrated circuit was the hallmark of the third generation of computers. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers.

Instead of punched cards and printouts, users interacted with third generation computers through keyboards and monitors and interfaced with an operating system, which allowed the device to run many different applications at one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors.

Fourth Generation (1971-Present) Microprocessors
The microprocessor brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip. What in the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004 chip, developed in 1971, located all the components of the computer—from the central processing unit and memory to input/output controls—on a single chip.

In 1981 IBM introduced its first computer for the home user, and in 1984 Apple introduced the Macintosh. Microprocessors also moved out of the realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors.

As these small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the Internet. Fourth generation computers also saw the development of GUIs, the mouse and handheld devices.

Fifth Generation (Present and Beyond) Artificial Intelligence
Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. The use of parallel processing and superconductors is helping to make artificial intelligence a reality. Quantum computation and molecular and nanotechnology will radically change the face of computers in years to come. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization

3. II, Computer sizes and power

Computers can be generally classified by size and power as follows, though there is considerable overlap:

• Personal computer: A small, single-user computer based on a microprocessor.
• Workstation: A powerful, single-user computer. A workstation is like a personal computer, but it has a more powerful microprocessor and, in general, a higher-quality monitor.
• Minicomputer: A multi-user computer capable of supporting up to hundreds of users simultaneously.
• Mainframe: A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously.
• Supercomputer: An extremely fast computer that can perform hundreds of millions of instructions per second.

Supercomputer and Mainframe

Supercomputer is a broad term for one of the fastest computers currently available. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations (number crunching). For example, weather forecasting requires a supercomputer. Other uses of supercomputers scientific simulations, (animated) graphics, fluid dynamic calculations, nuclear energy research, electronic design, and analysis of geological data (e.g. in petrochemical prospecting). Perhaps the best known supercomputer manufacturer is Cray Research.

Mainframe was a term originally referring to the cabinet containing the central processor unit or "main frame" of a room-filling Stone Age batch machine. After the emergence of smaller "minicomputer" designs in the early 1970s, the traditional big iron machines were described as "mainframe computers" and eventually just as mainframes. Nowadays a Mainframe is a very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. The chief difference between a supercomputer and a mainframe is that a supercomputer channels all its power into executing a few programs as fast as possible, whereas a mainframe uses its power to execute many programs concurrently. In some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program faster than a mainframe. The distinction between small mainframes and minicomputers is vague, depending really on how the manufacturer wants to market its machines.

Minicomputer

It is a midsize computer. In the past decade, the distinction between large minicomputers and small mainframes has blurred, however, as has the distinction between small minicomputers and workstations. But in general, a minicomputer is a multiprocessing system capable of supporting from up to 200 users simultaneously.

Workstation

It is a type of computer used for engineering applications (CAD/CAM), desktop publishing, software development, and other types of applications that require a moderate amount of computing power and relatively high quality graphics capabilities. Workstations generally come with a large, high-resolution graphics screen, at large amount of RAM, built-in network support, and a graphical user interface. Most workstations also have a mass storage device such as a disk drive, but a special type of workstation, called a diskless workstation, comes without a disk drive. The most common operating systems for workstations are UNIX and Windows NT. Like personal computers, most workstations are single-user computers. However, workstations are typically linked together to form a local-area network, although they can also be used as stand-alone systems.

N.B.: In networking, workstation refers to any computer connected to a local-area network. It could be a workstation or a personal computer.

Personal computer:

It can be defined as a small, relatively inexpensive computer designed for an individual user. In price, personal computers range anywhere from a few hundred pounds to over five thousand pounds. All are based on the microprocessor technology that enables manufacturers to put an entire CPU on one chip. Businesses use personal computers for word processing, accounting, desktop publishing, and for running spreadsheet and database management applications. At home, the most popular use for personal computers is for playing games and recently for surfing the Internet.

Personal computers first appeared in the late 1970s. One of the first and most popular personal computers was the Apple II, introduced in 1977 by Apple Computer. During the late 1970s and early 1980s, new models and competing operating systems seemed to appear daily. Then, in 1981, IBM entered the fray with its first personal computer, known as the IBM PC. The IBM PC quickly became the personal computer of choice, and most other personal computer manufacturers fell by the wayside. P.C. is short for personal computer or IBM PC. One of the few companies to survive IBM's onslaught was Apple Computer, which remains a major player in the personal computer marketplace. Other companies adjusted to IBM's dominance by building IBM clones, computers that were internally almost the same as the IBM PC, but that cost less. Because IBM clones used the same microprocessors as IBM PCs, they were capable of running the same software. Over the years, IBM has lost much of its influence in directing the evolution of PCs. Therefore after the release of the first PC by IBM the term PC increasingly came to mean IBM or IBM-compatible personal computers, to the exclusion of other types of personal computers, such as Macintoshes. In recent years, the term PC has become more and more difficult to pin down. In general, though, it applies to any personal computer based on an Intel microprocessor, or on an Intel-compatible microprocessor. For nearly every other component, including the operating system, there are several options, all of which fall under the rubric of PC

Today, the world of personal computers is basically divided between Apple Macintoshes and PCs. The principal characteristics of personal computers are that they are single-user systems and are based on microprocessors. However, although personal computers are designed as single-user systems, it is common to link them together to form a network. In terms of power, there is great variety. At the high end, the distinction between personal computers and workstations has faded. High-end models of the Macintosh and PC offer the same computing power and graphics capability as low-end workstations by Sun Microsystems, Hewlett-Packard, and DEC.

III, Personal Computer Types

Actual personal computers can be generally classified by size and chassis / case. The chassis or case is the metal frame that serves as the structural support for electronic components. Every computer system requires at least one chassis to house the circuit boards and wiring. The chassis also contains slots for expansion boards. If you want to insert more boards than there are slots, you will need an expansion chassis, which provides additional slots. There are two basic flavors of chassis designs–desktop models and tower models–but there are many variations on these two basic types. Then come the portable computers that are computers small enough to carry. Portable computers include notebook and subnotebook computers, hand-held computers, palmtops, and PDAs.

Tower model

The term refers to a computer in which the power supply, motherboard, and mass storage devices are stacked on top of each other in a cabinet. This is in contrast to desktop models, in which these components are housed in a more compact box. The main advantage of tower models is that there are fewer space constraints, which makes installation of additional storage devices easier.

Desktop model

A computer designed to fit comfortably on top of a desk, typically with the monitor sitting on top of the computer. Desktop model computers are broad and low, whereas tower model computers are narrow and tall. Because of their shape, desktop model computers are generally limited to three internal mass storage devices. Desktop models designed to be very small are sometimes referred to as slimline models.

Notebook computer

An extremely lightweight personal computer. Notebook computers typically weigh less than 6 pounds and are small enough to fit easily in a briefcase. Aside from size, the principal difference between a notebook computer and a personal computer is the display screen. Notebook computers use a variety of techniques, known as flat-panel technologies, to produce a lightweight and non-bulky display screen. The quality of notebook display screens varies considerably. In terms of computing power, modern notebook computers are nearly equivalent to personal computers. They have the same CPUs, memory capacity, and disk drives. However, all this power in a small package is expensive. Notebook computers cost about twice as much as equivalent regular-sized computers. Notebook computers come with battery packs that enable you to run them without plugging them in. However, the batteries need to be recharged every few hours.

Laptop computer

A small, portable computer -- small enough that it can sit on your lap. Nowadays, laptop computers are more frequently called notebook computers.

Subnotebook computer

A portable computer that is slightly lighter and smaller than a full-sized notebook computer. Typically, subnotebook computers have a smaller keyboard and screen, but are otherwise equivalent to notebook computers.

Hand-held computer

A portable computer that is small enough to be held in one’s hand. Although extremely convenient to carry, handheld computers have not replaced notebook computers because of their small keyboards and screens. The most popular hand-held computers are those that are specifically designed to provide PIM (personal information manager) functions, such as a calendar and address book. Some manufacturers are trying to solve the small keyboard problem by replacing the keyboard with an electronic pen. However, these pen-based devices rely on handwriting recognition technologies, which are still in their infancy. Hand-held computers are also called PDAs, palmtops and pocket computers.

Palmtop

A small computer that literally fits in your palm. Compared to full-size computers, palmtops are severely limited, but they are practical for certain functions such as phone books and calendars. Palmtops that use a pen rather than a keyboard for input are often called hand-held computers or PDAs. Because of their small size, most palmtop computers do not include disk drives. However, many contain PCMCIA slots in which you can insert disk drives, modems, memory, and other devices. Palmtops are also called PDAs, hand-held computers and pocket computers.

PDA

Short for personal digital assistant, a handheld device that combines computing, telephone/fax, and networking features. A typical PDA can function as a cellular phone, fax sender, and personal organizer. Unlike portable computers, most PDAs are pen-based, using a stylus rather than a keyboard for input. This means that they also incorporate handwriting recognition features. Some PDAs can also react to voice input by using voice recognition technologies. The field of PDA was pioneered by Apple Computer, which introduced the Newton MessagePad in 1993. Shortly thereafter, several other manufacturers offered similar products. To date, PDAs have had only modest success in the marketplace, due to their high price tags and limited applications. However, many experts believe that PDAs will eventually become common gadgets.

PDAs are also called palmtops, hand-held computers and pocket computers.

 

4. What is a CPU?

CPU is an acronym that stands for central processing unit. The central processing unit is responsible for performing all of the mathematical calculations that are required for a computer to function properly. Because a computer cannot function without the CPU (which may also be referred to as the central processor or just the processor), it is not uncommon to hear people refer to the CPU as the "brains" of a computer.

ALU - Arithmetic Logic Unit

The ALU (Arithmetic Logic Unit) is an internal part of the processor which is used for all mathematical and logical operations, the basic operations of an ALU include adding and multiplying binary values as well as performing logical operations such as AND, OR and XOR.

The algorithms for performing these mathematical and logical operations are hard coded (stored permanently) within the ALU.


Control Unit
The control unit is the circuitry that controls the flow of information through the processor, and coordinates the activities of the other units within it. In a way, it is the "brain within the brain", as it controls what happens inside the processor, which in turn controls the rest of the PC.
The functions performed by the control unit vary greatly by the internal architecture of the CPU, since the control unit really implements this architecture. On a regular processor that executes x86 instructions natively, the control unit performs the tasks of fetching, decoding, managing execution and then storing results. On a processor with a RISC core the control unit has significantly more work to do. It manages the translation of x86 instructions to RISC micro-instructions, manages scheduling the micro-instructions between the various execution units, and juggles the output from these units to make sure they end up where they are supposed to go. On one of these processors the control unit may be broken into other units (such as a scheduling unit to handle scheduling and a retirement unit to deal with results coming from the pipeline) due to the complexity of the job it must perform.

memory Last modified: Wednesday, February 27, 2008

Internal storage areas in the computer. The term memory identifies data storage that comes in the form of chips, and the word storage is used for memory that exists on tapes or disks. Moreover, the term memory is usually used as a shorthand for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk. Every computer comes with a certain amount of physical memory, usually referred to as main memory or RAM. You can think of main memory as an array of boxes, each of which can hold a single byte of information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters) of information. There are several different types of memory: ·  RAM (random-access memory): This is the same as main memory. When used by itself, the term RAM refers to read and write memory; that is, you can both write data into RAM and read data from RAM. This is in contrast to ROM, which permits you only to read data. Most RAM is volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon as the power is turned off, whatever data was in RAM is lost. ·  ROM (read-only memory): Computers almost always contain a small amount of read-only memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written to. ·  PROM (programmable read-only memory): A PROM is a memory chip on which you can store a program. But once the PROM has been used, you cannot wipe it clean and use it to store something else. Like ROMs, PROMs are non-volatile. ·  EPROM (erasable programmable read-only memory): An EPROM is a special type of PROM that can be erased by exposing it to ultraviolet light. ·  EEPROM (electrically erasable programmable read-only memory): An EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge.

input device Last modified: Friday, September 18, 2009

Any machine that feeds data into a computer. For example, a keyboard is an input device, whereas a display monitor is an output device. Input devices other than the keyboard are sometimes called alternate input devices. Mice, trackballs, and light pens are all alternate input devices.

output device Last modified: Thursday, August 30, 2001

Any machine capable of representing information from a computer. This includes display screens, printers, plotters, and synthesizers.

Different Types of Operating Systems

Operating systems that create a link between users and the applications form the core of computer systems. It dissociates the programs and the hardware and simplifies resource management. Let us look at the different types of operating systems.

An operating system is a software component of a computer system that is responsible for the management of various activities of the computer and the sharing of computer resources. It hosts the several applications that run on a computer and handles the operations of computer hardware. Users and application programs access the services offered by the operating systems, by means of system calls and application programming interfaces. Users interact with operating systems through Command Line Interfaces (CLIs) or Graphical User Interfaces known as GUIs. In short, operating system enables user interaction with computer systems by acting as an interface between users or application programs and the computer hardware. Here is an overview of the different types of operating systems.

Real-time Operating System: It is a multitasking operating system that aims at executing real-time applications. Real-time operating systems often use specialized scheduling algorithms so that they can achieve a deterministic nature of behavior. The main object of real-time operating systems is their quick and predictable response to events. They either have an event-driven or a time-sharing design. An event-driven system switches between tasks based of their priorities while time-sharing operating systems switch tasks based on clock interrupts.

Multi-user and Single-user Operating Systems: The operating systems of this type allow a multiple users to access a computer system concurrently. Time-sharing system can be classified as multi-user systems as they enable a multiple user access to a computer through the sharing of time. Single-user operating systems, as opposed to a multi-user operating system, are usable by a single user at a time. Being able to have multiple accounts on a Windows operating system does not make it a multi-user system. Rather, only the network administrator is the real user. But for a Unix-like operating system, it is possible for two users to login at a time and this capability of the OS makes it a multi-user operating system.

Multi-tasking and Single-tasking Operating Systems: When a single program is allowed to run at a time, the system is grouped under a single-tasking system, while in case the operating system allows the execution of multiple tasks at one time, it is classified as a multi-tasking operating system. Multi-tasking can be of two types namely, pre-emptive or co-operative. In pre-emptive multitasking, the operating system slices the CPU time and dedicates one slot to each of the programs. Unix-like operating systems such as Solaris and Linux support pre-emptive multitasking. Cooperative multitasking is achieved by relying on each process to give time to the other processes in a defined manner. MS Windows prior to Windows 95 used to support cooperative multitasking.

Distributed Operating System: An operating system that manages a group of independent computers and makes them appear to be a single computer is known as a distributed operating system. The development of networked computers that could be linked and communicate with each other, gave rise to distributed computing. Distributed computations are carried out on more than one machine. When computers in a group work in cooperation, they make a distributed system.

Embedded System: The operating systems designed for being used in embedded computer systems are known as embedded operating systems. They are designed to operate on small machines like PDAs with less autonomy. They are able to operate with a limited number of resources. They are very compact and extremely efficient by design. Windows CE, FreeBSD and Minix 3 are some examples of embedded operating systems.

The operating systems thus contribute to the simplification of the human interaction with the computer hardware. They are responsible for linking application programs with the hardware, thus achieving an easy user access to the computers.

As computers have progressed and developed so have the types of operating systems. Below is a basic list of the different types of operating systems and a few examples of operating systems that fall into each of the categories. Many computer operating systems will fall into more than one of the below categories. GUI - Short for Graphical User Interface, a GUI Operating System contains graphics and icons and is commonly navigated by using a computer mouse. See our GUI dictionary definition for a complete definition. Below are some examples of GUI Operating Systems. System 7.x Windows 98 Windows CE Multi-user - A multi-user operating system allows for multiple users to use the same computer at the same time and/or different times. See our multi-user dictionary definition for a complete definition for a complete definition. Below are some examples of multi-user operating systems. Linux Unix Windows 2000 Multiprocessing - An operating system capable of supporting and utilizing more than one computer processor. Below are some examples of multiprocessing operating systems. Linux Unix Windows 2000 Multitasking - An operating system that is capable of allowing multiple software processes to run at the same time. Below are some examples of multitasking operating systems. Unix Windows 2000 Multithreading - Operating systems that allow different parts of a software program to run concurrently. Operating systems that would fall into this category are: Linux Unix Windows 2000 Troubleshooting Common questions and answers to operating systems in general can be found on the below operating system question and answers. All other questions relating to an operating system in particular can be found through the operating system page. Linux / Variants MacOS MS-DOS IBM OS/2 Warp Unix / Variants Windows CE Windows 3.x Windows 95 Windows 98 Windows 98 SE Windows ME Windows NT Windows 2000 Windows XP Windows Vista

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Operating system listing

Below is a listing of many of the different types of operating systems available today, the dates they were released, the platforms they have been developed for and who developed them.

Operating system	Date first released	Platform	Developer
AIX / AIXL	Unix / Linux history can be found here.	Various	IBM
AmigaOS	Currently no AmigaOS operating system history.	Amiga	Commodore
BSD	Unix / Linux history can be found here.	Various	BSD
Caldera Linux	Unix / Linux history can be found here.	Various	SCO
Corel Linux	Unix / Linux history can be found here.	Various	Corel
Debian Linux`	Unix / Linux history can be found here.	Various	GNU
DUnix	Unix / Linux history can be found here.	Various	Digital
DYNIX/ptx	Unix / Linux history can be found here.	Various	IBM
HP-UX	Unix / Linux history can be found here.	Various	Hewlett Packard
IRIX	Unix / Linux history can be found here.	Various	SGI
Kondara Linux	Unix / Linux history can be found here.	Various	Kondara
Linux	Unix / Linux history can be found here.	Various	Linus Torvalds
MAC OS 8	Apple operating system history can be found here.	Apple Macintosh	Apple
MAC OS 9	Apple operating system history can be found here.	Apple Macintosh	Apple
MAC OS 10	Apple operating system history can be found here.	Apple Macintosh	Apple
MAC OS X	Apple operating system history can be found here.	Apple Macintosh	Apple
Mandrake Linux	Unix / Linux history can be found here.	Various	Mandrake
MINIX	Unix / Linux history can be found here.	Various	MINIX
MS-DOS 1.x	MS-DOS history can be found here.	IBM / PC	Microsoft
MS-DOS 2.x	MS-DOS history can be found here.	IBM / PC	Microsoft
MS-DOS 3.x	MS-DOS history can be found here.	IBM / PC	Microsoft
MS-DOS 4.x	MS-DOS history can be found here.	IBM / PC	Microsoft
MS-DOS 5.x	MS-DOS history can be found here.	IBM / PC	Microsoft
MS-DOS 6.x	MS-DOS history can be found here.	IBM / PC	Microsoft
NEXTSTEP	Apple operating system history can be found here.	Various	Apple
OSF/1	Unix / Linux history can be found here.	Various	OSF
QNX	Unix / Linux history can be found here.	Various	QNX
Red Hat Linux	Unix / Linux history can be found here.	Various	Red Hat
SCO	Unix / Linux history can be found here.	Various	SCO
Slackware Linux	Unix / Linux history can be found here.	Various	Slackware
Sun Solaris	Unix / Linux history can be found here.	Various	Sun
SuSE Linux	Unix / Linux history can be found here.	Various	SuSE
System 1	Apple operating system history can be found here.	Apple Macintosh	Apple
System 2	Apple operating system history can be found here.	Apple Macintosh	Apple
System 3	Apple operating system history can be found here.	Apple Macintosh	Apple
System 4	Apple operating system history can be found here.	Apple Macintosh	Apple
System 6	Apple operating system history can be found here.	Apple Macintosh	Apple
System 7	Apple operating system history can be found here.	Apple Macintosh	Apple
System V	Unix / Linux history can be found here.	Various	System V
Tru64 Unix	Unix / Linux history can be found here.	Various	Digital
Turbolinux	Unix / Linux history can be found here.	Various	Turbolinux
Ultrix	Unix / Linux history can be found here.	Various	Ultrix
Unisys	Unix / Linux history can be found here.	Various	Unisys
Unix	Unix / Linux history can be found here.	Various	Bell labs
UnixWare	Unix / Linux history can be found here.	Various	UnixWare
VectorLinux	Unix / Linux history can be found here.	Various	VectorLinux
Windows 2000	Windows history can be found here.	IBM / PC	Microsoft
Windows 2003	Windows history can be found here.	IBM / PC	Microsoft
Windows 3.X	Windows history can be found here.	IBM / PC	Microsoft
Windows 95	Windows history can be found here.	IBM / PC	Microsoft
Windows 98	Windows history can be found here.	IBM / PC	Microsoft
Windows CE	Windows history can be found here.	PDA	Microsoft
Windows ME	Windows history can be found here.	IBM / PC	Microsoft
Windows NT	Windows history can be found here.	IBM / PC	Microsoft
Windows Vista	Windows history can be found here.	IBM / PC	Microsoft
Windows XP	Windows history can be found here.	IBM / PC	Microsoft
Xenix	Unix / Linux history can be found here.	Various	Microsoft

DOS Last modified: Friday, December 14, 2001

(1) Acronym for disk operating system. The term DOS can refer to any operating system, but it is most often used as a shorthand for MS-DOS (Microsoft disk operating system). Originally developed by Microsoft for IBM, MS-DOS was the standard operating system for IBM-compatible personal computers. The initial versions of DOS were very simple and resembled another operating system called CP/M. Subsequent versions have became increasingly sophisticated as they incorporated features of minicomputer operating systems. However, DOS is still a 16-bit operating system and does not support multiple users or multitasking. For some time, it has been widely acknowledged that DOS is insufficient for modern computer applications. Microsoft Windows helped alleviate some problems, but still, it sat on top of DOS and relied on DOS for many services. Even Windows 95 sat on top of DOS. Newer operating systems, such as Windows NT and OS/2 Warp, do not rely on DOS to the same extent, although they can execute DOS-based programs. It is expected that as these operating systems gain market share, DOS will eventually disappear. In the meantime, Caldera, Inc. markets a version of DOS called DR-OpenDOS that extends MS-DOS in significant ways.

application software Last modified: Wednesday, February 12, 2003

A program or group of programs designed for end users. Software can be divided into two general classes: systems software and applications software. Systems software consists of low-level programs that interact with the computer at a very basic level. This includes operating systems, compilers, and utilities for managing computer resources. In contrast, applications software (also called end-user programs) includes database programs, word processors, and spreadsheets. Figuratively speaking, applications software sits on top of systems software because it is unable to run without the operating system and system utilities. Also see a diagram of n-tier application architecture in the quick reference section of Webopedia.

word processing Last modified: Friday, September 18, 2009

Using a computer to create, edit, and print documents. Of all computer applications, word processing is the most common. To perform word processing, you need a computer, a special program called a word processor, and a printer. A word processor enables you to create a document, store it electronically on a disk, display it on a screen, modify it by entering commands and characters from the keyboard, and print it on a printer. The great advantage of word processing over using a typewriter is that you can make changes without retyping the entire document. If you make a typing mistake, you simply back up the cursor and correct your mistake. If you want to delete a paragraph, you simply remove it, without leaving a trace. It is equally easy to insert a word, sentence, or paragraph in the middle of a document. Word processors also make it easy to move sections of text from one place to another within a document, or between documents. When you have made all the changes you want, you can send the file to a printer to get a hardcopy. Word processors vary considerably, but all word processors support the following basic features: ·  insert text: Allows you to insert text anywhere in the document. ·  delete text: Allows you to erase characters, words, lines, or pages as easily as you can cross them out on paper. ·  cut and paste : Allows you to remove (cut) a section of text from one place in a document and insert (paste) it somewhere else. ·  copy : Allows you to duplicate a section of text. ·  page size and margins : Allows you to define various page sizes and margins, and the word processor will automatically readjust the text so that it fits. ·  search and replace : Allows you to direct the word processor to search for a particular word or phrase. You can also direct the word processor to replace one group of characters with another everywhere that the first group appears. ·  word wrap : The word processor automatically moves to the next line when you have filled one line with text, and it will readjust text if you change the margins. ·  print: Allows you to send a document to a printer to get hardcopy. Word processors that support only these features (and maybe a few others) are called text editors. Most word processors, however, support additional features that enable you to manipulate and format documents in more sophisticated ways. These more advanced word processors are sometimes called full-featured word processors. Full-featured word processors usually support the following features: ·  file management : Many word processors contain file management capabilities that allow you to create, delete, move, and search for files. ·  font specifications: Allows you to change fonts within a document. For example, you can specify bold, italics, and underlining. Most word processors also let you change the font size and even the typeface. ·  footnotes and cross-references: Automates the numbering and placement of footnotes and enables you to easily cross-reference other sections of the document. ·  graphics graphics: Allows you to embed illustrations and graphs into a document. Some word processors let you create the illustrations within the word processor; others let you insert an illustration produced by a different program. ·  headers , footers , and page numbering: Allows you to specify customized headers and footers that the word processor will put at the top and bottom of every page. The word processor automatically keeps track of page numbers so that the correct number appears on each page. ·  layout : Allows you to specify different margins within a single document and to specify various methods for indenting paragraphs. ·  macros : A macro is a character or word that represents a series of keystrokes. The keystrokes can represent text or commands. The ability to define macros allows you to save yourself a lot of time by replacing common combinations of keystrokes. ·  merges: Allows you to merge text from one file into another file. This is particularly useful for generating many files that have the same format but different data. Generating mailing labels is the classic example of using merges. ·  spell checker : A utility that allows you to check the spelling of words. It will highlight any words that it does not recognize. ·  tables of contents and indexes: Allows you to automatically create a table of contents and index based on special codes that you insert in the document. ·  thesaurus: A built-in thesaurus that allows you to search for synonyms without leaving the word processor. ·  windows : Allows you to edit two or more documents at the same time. Each document appears in a separate window. This is particularly valuable when working on a large project that consists of several different files. ·  WYSIWYG (what you see is what you get): With WYSIWYG, a document appears on the display screen exactly as it will look when printed. The line dividing word processors from desktop publishing systems is constantly shifting. In general, though, desktop publishing applications support finer control over layout, and more support for full-color documents.

spreadsheet Last modified: Friday, May 16, 2003

A table of values arranged in rows and columns. Each value can have a predefined relationship to the other values. If you change one value, therefore, you may need to change other values as well. Spreadsheet applications (sometimes referred to simply as spreadsheets) are computer programs that let you create and manipulate spreadsheets electronically. In a spreadsheet application, each value sits in a cell. You can define what type of data is in each cell and how different cells depend on one another. The relationships between cells are called formulas, and the names of the cells are called labels. Once you have defined the cells and the formulas for linking them together, you can enter your data. You can then modify selected values to see how all the other values change accordingly. This enables you to study various what-if scenarios. A simple example of a useful spreadsheet application is one that calculates mortgage payments for a house. You would define five cells: ·  1. total cost of the house ·  2. down payment ·  3. mortgage rate ·  4. mortgage term ·  5. monthly payment Once you had defined how these cells depend on one another, you could enter numbers and play with various possibilities. For example, keeping all the other values the same, you could see how different mortgage rates would affect your monthly payments. There are a number of spreadsheet applications on the market, Lotus 1-2-3 and Excel being among the most famous. The more powerful spreadsheet applications support graphics features that enable you to produce charts and graphs from the data. Most spreadsheet applications are multidimensional, meaning that you can link one spreadsheet to another. A three-dimensional spreadsheet, for example, is like a stack of spreadsheets all connected by formulas. A change made in one spreadsheet automatically affects other spreadsheets.

What is Presentation?

Presentation runs neurobehavioral experiments.

Presentation is a stimulus delivery and experimental control software system for neuroscience. Presentation runs on Windows and uses standard PC hardware. Presentation was designed for behavioral and physiological experiments that collect fMRI, ERP, MEG, reaction time, and electrophysiological (e.g. single neuron) data. At the same time, Presentation is very flexible and has many features that make it applicable to a diverse range of applications (see Features). Presentation is designed to provide the best possible timing accuracy and timing verification on standard hardware (see Timing Overview). Presentation is also completely programmable (see PCL Programming).

Presentation was created by neuroscientists.

Presentation grew out of an active research lab doing ERP and fMRI studies using very demanding paradigms. Presentation development was originally supported by NINDS (National Institute of Neurological Disorders and Stroke), and is currently supported by sales. Presentation's rapid development continues to be guided by the needs of, and feedback from, our large group of users (see Development).
You can purchase Presentation from the NBS website (http://www.neurobs.com). Or try it out first: every new user gets a free trial license for the full software package. Technical support for Presentation is always available on the NBS forums (http://www.neurobs.com/chatter_box).

What is Electronic Mail?
Electronic mail, or e-mail (and mail) for short, is one of the most popular uses of the Internet. Once you have an e-mail account you can send an electronic message (sort of like a letter) to just about anyone else with an e-mail account so long as you know their e-mail address.
If you have an internet service provider (ISP) or commercial online service you probably already have and know your e-mail address (If you don't know it, you can always badger technical support!) Most e-mail addresses are set up like this: it is your username, then an @ ('at') symbol, and then a domain name (something .com, .net, or .org in most cases).
For example, if you are on America Online (AOL) your e-mail address is username@aol.com where username is your AOL screen name. (Contrary to popular belief, not everyone uses AOL, so if you use AOL and someone asks you for your e-mail address, always remember to add the @aol.com part or they might get an error message!)
Using e-mail is rather straightforward. Once you have an account set up, you just select the option that says something like "new e-mail message" or "create a new message". You'll probably be prompted with three boxes (called fields):

• To:
• Subject:
• Body: (sometimes the body doesn't actually say body, it's just the big area where you type your actual message.)

In the To: field you type the complete e-mail address of the person who will receive the e-mail. You can type anything you want as the subject and body, although the length of the subject is limited. You usually want to keep the subject to just a few words describing the content of the body of the e-mail message.
You may also see options for attachments and forwards. You can add files to your e-mail by using the attachment option. You can forward (make a copy) of a message you receive from someone (if you have their permission if necessary) and mail it to someone else with the forward option.
You may also see fields for CC: and BCC: close to your To: field. CC stands for carbon copy. If you want to send a message to multiple people, add the extra people in the CC: field (usually you separate their e-mail addresses by commas). BCC stands for blind carbon copy. BCC works just like a carbon copy, except the e-mail addresses you type in BCC do not show up to the other recipients. (Example: You send a message To: Mary and BCC: Joey. Joey will see Mary's e-mail address, but Mary won't see Joey's e-mail address because you "blinded" it by putting it in the BCC field.)
There are two things about file attachments you need to be careful of. The first thing is that you need to limit the size of files you are sending. An attachment the size of a floppy disk (1.44MB) can take anywhere from a few seconds to a few hours for someone to receive, depending on the speed of their Internet connection. Get permission before sending large files to someone.
The second reason you need to be careful with attachments is because they are one of the most common ways for computer viruses to spread. As a rule you should never open an attachment from someone you don't know or don't trust. And even if you know the sender, don't open an attachment you are not expecting or an attachment that looks suspicious. Some viruses can destroy all the data on your computer so it's best to play it safe.
CAUTION: You can also get viruses by downloading executable files (usually .com and .exe on Windows computers) from web sites. While only a very small percentage of executable files contain viruses you still may get one. Don't download or run executable files from web sites you don't trust.

Web browser definition - computer

The program that serves as your front end to the Web on the Internet. In order to view a site, you type its address (URL) into the browser's Location field; for example, www.computerlanguage.com, and the home page of that site is downloaded to you. The home page is an index to other pages on that site that you can jump to by clicking an underlined hyperlink or an icon. Links on that site may take you to other related sites.
Bookmarks
Browsers have a Bookmark or Favorites feature that lets you store references to your favorite sites. Instead of having to type in the URL to visit the site again, you select the bookmark.
It Started with Mosaic
The Mosaic browser put the Web on the map in 1993, but by the mid-1990s, Netscape Navigator (commonly called "Netscape") had 80% of the market. Vying for top spot, Netscape and Microsoft's Internet Explorer (IE) constantly added new features and functions that fragmented Web sites into competing camps.

As of mid-2008, IE, which is included with every Windows PC, has approximately 74% of the market, while Firefox has 18%. Safari comes in third with 6%, and Opera and Netscape each have less than 1%. Google entered the Web browser arena in late 2008 and is expected to grab a fair share (see Google Chrome).
Best Viewed By...
In the early days of the Web, there was a feature battle, and sites would often say "best viewed by Netscape" or "best viewed by Internet Explorer." This notice is rarely seen today as all browsers support standards that render most Web pages the same. See Mosaic, Opera, Firefox, Mozilla, Safari, Google Chrome, Maxthon, hyperlink, World Wide Web, HTML and microbrowser.

search engine Last modified: Thursday, October 23, 2008

A program that searches documents for specified keywords and returns a list of the documents where the keywords were found. Although search engine is really a general class of programs, the term is often used to specifically describe systems like Google,  Alta Vista and Excite that enable users to search for documents on the World Wide Web and USENET newsgroups. Typically, a search engine works by sending out a spider to fetch as many documents as possible. Another program, called an indexer, then reads these documents and creates an index based on the words contained in each document. Each search engine uses a proprietary algorithm to create its indices such that, ideally, only meaningful results are returned for each query. See How Web Search Engines Work in the Did You Know...? section of Webopedia. Also see "Web Search Engines & Directories" in the Quick Reference section of Webopedia.

The Most Well Known

Internet Explorer and Netscape are the two major browsers used to access the Web. Similar in features and function, each new version includes enhancements that the other generally catches up to in its next release. (Web page examples courtesy of Pyramid Studios, www.artistexpo.com)

e-services

- E-services, a business concept developed by Hewlett Packard (HP), is the idea that the World Wide Web is moving beyond e-business and e-commerce (that is, completing sales on the Web) into a new phase where many business services can be provided for a business or consumer using the Web. Some e-services, such as remote bulk printing, may be done at a Web site; other e-services, such as news updates to subscribers, may be sent to your computer. Other e-services will be done in the background without the customer's immediate knowledge. HP defines e-services as "modular, nimble, electronic services that perform work, achieve tasks, or complete transactions." Using HP's e-services concept, any application program or information resource is a potential e-service and Internet service providers (ISPs) and other companies are logical distributors or access points for such services. The e-services concept also sees services being built into "cars, networked devices, and virtually anything that has a microchip in it." HP's vision is that IT departments will increasingly address their needs in a modular way so that individual modules can potentially be addressed by some e-service. HP notes three trends: The increasing availability of "apps-on-tap" - for accounting, payment systems, purchasing, and enterprise resource planning (ERP). (HP offers several of these services.) An increase in the number of specialized Web portal sites such as OpenSkies (travel services) and Ariba.com's e-procurement services. More on-the-fly handling of service requests that may require handling by several companies. HP sees its e-speak application development facilities as supporting e-services. Also see application service provider (ASP).