19-10-2012, 04:52 PM
Introduction to Computers
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Introduction:
» The modern computer, which we are using today, is not the invention of a single individual. It is the result of
countless inventions, ideas and developments made by many people throughout the last several decades.
» The history of automatic data processing begins with Charles Babbage’s attempt to build a mechanical
calculator at Cambridge, England, in 1830.
» By the end of 1930, punched cards were in wide use in many businesses.
» In 1937, Howard Aiken, at Harvard, proposed to IBM that a machine could be constructed which would
automatically sequence the operations and perform calculations. That was the origin for the development
of automatic computers.
First Generation Computers: (1946 to 1959)
» UNIVAC (Universal Automatic Computer) was the first general purpose electrical computer.
» These computers employed vacuum tubes.
» These computers were large in size and required air conditioning (as they produce huge heat).
» The input and output units were punched cards.
» The input and output devices were very slow when compared to the speed of CPU.
» They were very expensive.
» The medium of internal storage was magnetic drum.
» Language used was Machine level language.
» Processors speed used to be measured in milliseconds.
» IBM-650 was the most popular first generation computer and was introduced in 1950 with magnetic drum
memory and punched cards for input and output respectively. It was intended (=designed) for both business
and scientific applications.
Second Generation Computers: (1959 to 1965)
» These computers employed transistors and other similar devices.
» Their circuits were smaller than vacuum tubes and generated less heat. Hence they required less power,
were faster and more reliable.
» There were two separate categories of second generation computers - for business & scientific applications.
» IBM 1401 was the most popular second-generation computer.
» They employed magnetic tape as input/output media.
» Main medium of internal storage was magnetic core memory.
» Language used was Assembly language.
» Processor speed started to be measured in microseconds.
Third Generation Computers: (1965 to 1970)
» They employed integrated circuits, in which all the elements of an electronic
circuit are integrated (=included) on a tiny silicon wafer.
» They were much cheaper and more reliable than second-generation computers.
» Their speed is high and can support variety of peripherals.
» They are based on the principles of standardization and compatibility.
» The secondary storage of a particular computer can be easily expanded.
» They can be used for both scientific and business applications.
Digital Computers:
» Digital computers represent data as numbers. Counting on fingers is the simplest form of digital computer.
Adding machines and pocket calculators are common examples of digital computers.
» They accept input from various input devices, convert them into numbers and perform
arithmetic or logical operations on such numbers.
» It is also capable of storing data, performing logical operations, editing, deleting, printing
the output etc.
» The accuracy is also high. Hence suitable for business data processing applications.
» Cost is comparatively higher than analog computers.
» Programming is complex in nature.
Hybrid computers:
Hybrid computers combine the best features of analog and digital computers. They have
the speed of analog computers and the accuracy of digital computers. They are used in areas where data from
analog devices is converted into digits & processed by computer.
For e.g. Analog devices measure patient’s vital signs like temperature, heart function etc. These are then
converted into numbers and supplied to digital components of the system. Now digital components of the
computer will process such data.