Analog Computer & Digital Computer

Analog computer

Computer in which continuously variable physical quantities, such as electrical potential, fluid pressure, or mechanical motion, are used to represent (analogously) the quantities in the problem to be solved. The analog system is set up according to initial conditions and then allowed to change freely. Answers to the problem are obtained by measuring the variables in the analog model. Analog computers are especially well suited to simulating dynamic systems; such simulations may be conducted in real time or at greatly accelerated rates, allowing experimentation by performing many runs with different variables. They have been widely used in simulating the operation of aircraft, nuclear power plants, and industrial chemical processes.



Polish Analog computer ELWAT

Digital computer

A digital computer is an electronic computing machine that uses the binary digits ( bits ) 0 and 1 to represent all forms of information internally in digital form. Every computer has a set of instructions that define the basic functions it can perform. Sequences of these instructions constitute machine-language programs that can be stored in the computer and used to tailor it to an essentially unlimited number of specialized applications. Calculators are small computers specialized for mathematical computations. General-purpose computers range from pocket-sized personal digital assistants (notepad computers), to medium-sized desktop computers (personal computers and workstations), to large, powerful computers that are shared by many users via a computer network. The vast majority of digital computers now in use are inexpensive, special-purpose microcontrollers that are embedded, often invisibly, in such devices as toys, consumer electronic equipment, and automobiles

Digital Computer

A device that processes numerical information; more generally, any device that manipulates symbolic information according to specified computational procedures. The term digital computer—or simply, computer—embraces calculators, computer workstations, control computers (controllers) for applications such as domestic appliances and industrial processes, data-processing systems, microcomputers, microcontrollers, multiprocessors, parallel computers, personal computers, network servers, and supercomputers.

Slide Rule

The slide rule is a mechanical analog computer, consisting of at least two finely divided scales (rules), most often a fixed outer pair and a movable inner one, with a sliding window called the cursor. The slide rule is used primarily for multiplication and division, and also for scientific functions such as roots, logarithms and trigonometry, but does not generally perform addition or subtraction. For example:

Abacus

An ,abacus also called a counting frame, is a calculating tool for performing arithmetic processes. Nowadays, abaci are often constructed as a wooden frame with beads sliding on wires, but originally they were beads or stones moved in grooves in sand or on tablets of wood, stone, or metal. The abacus was in use centuries before the adoption of the written modern numeral system and is still widely used by merchants and clerks in China, Japan, Africa, India and elsewhere.

Computer

It is a programmable machine.

The two main principal characteristics of a computers are:

It responds to a specific set of instructions in a well-defined manner.

• It can execute a prerecorded list of instructions .

Modern computers are electronic and digital. The actual machineries are ( wires, transistors, and circuits) called hardware; And the instructions and data are called software.

All general-purpose computers require the following hardware Components:

Memory : Enables a computer to store, at least temporarily, data and programs.

Mass Storage Device : Allows a computer to permanently retain large amounts of data. Common mass storage devices include disk drives and tape drives.

Input Device : Usually a keyboard and mouse, the input device is the conduit through which data and instructions enter a computer.

Output Device : A display screen, printer, or other device that lets you see what the computer has accomplished.

Central Processing Unit (CPU): The heart of the computer, this is the component that actually executes instructions.

In addition to these components, many others make it possible for the basic components to work together efficiently. For example, every computer requires a bus that transmits data from one part of the computer to another.

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. In addition to the microprocessor a personal computer has a keyboard for entering data, a monitor for displaying information, and a storage device for saving data.

Workstation : A powerful, single-user computer. A workstation is like a personal computer, but it has a more powerful microprocessor and a higher-quality monitor.

Minicomputer : A multi-user computer capable of supporting from 10 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.

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.

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

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.

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.

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