Friday, March 20, 2009

Human Computer

Before computers became commercially available, the term Computer , in use from the mid 17th century, literally meant one who computes: a person performing mathematical calculations. Teams of people were frequently used to undertake long and often tedious calculations; the work was divided so that this could be done in parallel.

Sunday, March 15, 2009

Mechanical Calculating Device

A calculator is a device for performing mathematical calculations, distinguished from a Computer generally by a limited problem domain and an interface optimized for interactive calculation rather than programming. Calculators can be hardware or software, and mechanical or electronic, and are often built into devices such as PDAs or mobile phones.

A basic calculator
A basic calculator

Modern electronic calculators are generally small (often pocket-sized) and usually inexpensive. In addition to general purpose calculators, there are those designed for specific markets; for example, there are scientific calculators which focus on advanced math like trigonometry and statistics. Modern calculators are more portable than most computers, though most PDAs (Personal digital assistants) are comparable in size to handheld calculators.

Saturday, March 7, 2009

History Of Computer

It is difficult to identify any one device as the earliest Computer, partly because the term Computer has been subject to varying interpretations over time. Originally, the term Computer referred to a person who performed numerical calculations (a human computer), often with the aid of a mechanical calculating device.

The history of the modern Computer begins with two separate technologies - that of automated calculation and that of programmability.

Examples of early mechanical calculating devices included the abacus, the slide rule and arguably the astrolabe and the Antikythera mechanism (which dates from about 150-100 BC). The end of the Middle Ages saw a re-invigoration of European mathematics and engineering, and Wilhelm Schickard's 1623 device was the first of a number of mechanical calculators constructed by European engineers. However, none of those devices fit the modern definition of a Computer because they could not be programmed.

Hero of Alexandria built a mechanical theater which performed a play lasting 10 minutes and was operated by a complex system of ropes and drums that might be considered to be a means of deciding which parts of the mechanism performed which actions - and when. This is the essence of programmability. In 1801, Joseph Marie Jacquard made an improvement to the textile loom that used a series of punched paper cards as a template to allow his loom to weave intricate patterns automatically. The resulting Jacquard loom was an important step in the development of computers because the use of punched cards to define woven patterns can be viewed as an early, albeit limited, form of programmability.

It was the fusion of automatic calculation with programmability that produced the first recognisable computers. In 1837, Charles Babbage was the first to conceptualize and design a fully programmable mechanical Computer that he called "The Analytical Engine(The Analytical Engine should not be confused with Babbage's difference engine which was a non-programmable mechanical calculator Or A Analytical Engine is a special-purpose mechanical digital calculator, designed to tabulate polynomial functions. Since logarithmic and trigonometric functions can be approximated by polynomials, such a machine is more general than it appears at first). Due to limited finances, and an inability to resist tinkering with the design, Babbage never actually built his Analytical Engine.

Large-scale automated data processing of punched cards was performed for the U.S. Census in 1890 by tabulating machines designed by Herman Hollerith and manufactured by the Computing Tabulating Recording Corporation, which later became IBM. By the end of the 19th century a number of technologies that would later prove useful in the realization of practical computers had begun to appear: the punched card, Boolean algebra, the vacuum tube (thermionic valve) and the teleprinter.

During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticated analog computers, which used a direct mechanical or electrical model of the problem as a basis for computation (Computation is a general term for any type of information processing that can be represented mathematically. This includes phenomena ranging from human thinking to calculations with a more narrow meaning). However, these were not programmable and generally lacked the versatility and accuracy of modern digital computers.

For more detail visit to Wikipedia