Types
of computers
Analog computers: it
is a form of computer that uses the continuously-changeable aspects of physical
fact such as electrical, mechanical, or hydraulic quantities to model the
problem being solved
Analog means
continuity of associated quantity just like an analog clock measures time by
means of the distance traveled by the hand of the distance traveled by the
distance traveled by the hand of the clock around a dial.
Examples:
. Thermometer
. Analog clock
. Speedometer
. Tire pressure
gauge
Computer: Definition
A computer is a
machine that can be programmed to manipulate symbols. Its principal
characteristics are:
- It responds to a specific set of
instructions in a well-defined manner.
- It can execute a prerecorded list of
instructions (a program).
- It can quickly store and retrieve large
amounts of data.
Therefore
computers can perform complex and repetitive procedures quickly, precisely and
reliably. Modern computers are electronic and digital. The actual machinery
(wires, transistors, and circuits) is called hardware; the instructions and
data are called software. All general-purpose computers require the following
hardware components:
- Central processing
unit (CPU): The heart of the computer, this is the component that actually
executes instructions organized in programs ("software") which
tell the computer what to do.
- Memory (fast,
expensive, short-term memory): Enables a computer to store, at least
temporarily, data, programs, and intermediate results.
- Mass storage device
(slower, cheaper, long-term memory): Allows a computer to permanently
retain large amounts of data and programs between jobs. 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.
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
Microcomputer
Microcomputer, an
electronic device with a microprocessor as its central processing unit (CPU).
Microcomputer was formerly a commonly used term for personal computers,
particularly any of a class of small digital computers whose CPU is contained
on a single integrated semiconductor chip. Thus, a microcomputer uses a single
microprocessor for its CPU, which performs all logic and arithmetic operations.
The system also contains a number of associated semiconductor chips that serve
as the main memory for storing program instructions and data and as interfaces
for exchanging data of this sort with peripheral equipment—namely, input/output
devices (e.g., keyboard, video display, and printer) and auxiliary storage
units. Smaller microcomputers first marketed in the 1970s contain a single chip
on which all CPU, memory, and interface circuits are integrated.
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
Mainframe
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.
Super computer
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.
Personal computers
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.
