Types of computers


A computer is one of the most brilliant inventions of mankind. Thanks to the computer technology, we were able to achieve an efficient storage and processing of data; we could rest our brains by employing computer memory capacities for storage of the information. Owing to computers, we have been able speed up daily work, carry out critical transactions and achieve accuracy and precision in work output. The computers of the earlier years were of the size of a large room and were required to consume huge amounts of electric power. However, with the advancing technology, computers have shrunk to the size of a small watch. Depending on the processing powers and sizes of computers, they have been classified under various types. Let us look at the classification of computers
Since the invention of computers from first generation and fourth generation computers, they have been classified according to their types and how they operate that is input, process and output information. Below you will get a brief discussion on various types of Computers.
Based on the operational principle of computers, they are categorized as analog computers and hybrid computers.

Analog Computers:
An analog computer is one which can perform multiple calculations at once and can cope with infinite fractions of numbers. The term analog does not relate to how the computer is powered and it is possible to have electronic analog computer. The characteristics of an analog computer mean it can be better than a digital computer at particular tasks.These are almost extinct today. These are different from a digital computer because an analog computer can perform several mathematical operations simultaneously. It uses continuous variables for mathematical operations and utilizes mechanical or electrical energy.
A computer is simply a machine which processes data in a set fashion or, to put it another way, calculates. Today most computers are digital and work by reducing all data to binary numbers before procesing. Analog computers go back thousands of years but vary from digital computers in only two fundamental ways.
 The first is that an analog computer works in parallel. This means it can carry out multiple tasks simultaneously. A digital computer, even though it may work considerably faster, can only perform one calculation at any one instant. The only way around this in a digital computer is parallel computing, where a single machine has multiple processors. Even then, programs must often be rewritten to take advantage of this.
The second difference is that an analog computer handles continuous variables, while a digital computer works with discrete numbers. The difference between these is that continuous variables can include every conceivable number, even irrational numbers. These are ones with infinite decimal fractions such as pi.

Hybrid Computers:
Hybrid computer is a digital computer that accepts analog signals, converts them to digital and processes them in digital form. This integration is obtained by digital to analog and analog to digital converter. A hybrid computer may use or produce analog data or digital data. It accepts a continuously varying input, which is then converted into a set of discrete values for digital processing. A hybrid computer system setup offers a cost-effective method of performing complex simulations. A hybrid computer capable of real-time solution has been less expensive than any equivalent digital computer. Hybrid computers have been necessary for successful system development. An example of a hybrid computer is the computer used in hospitals to measure the heartbeat of the patient. Hybrid Machines are generally used in scientific applications or in controlling industrial processes.
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A combination of computers that are capable of inputting and outputting in both digital and analog signals. A hybrid computer system setup offers a cost effective method of performing complex simulations. 
 
Hybrid computer  are computer that are designed to provide functions and features that are found with both analog computers and digital computers. The idea behind this combined or Hybrid computer model is to create a working unit that offers the best of both types of computers. With most designs, the analog components of the equipment provide efficient processing of differential equations, while the digital aspects of the computer address the logical operations associated with the system.
By creating this type of integrated computer, the benefits of both analog and digital computing are readily available. A hybrid computer is extremely fast when it comes to managing equations, even when those calculations are extremely complicated. This advantage is made possible by the presence of the analog components inherent within the design of the equipment.
While the hybrid computer can manage equations with the same ease as an analog computer, the digital components help to eliminate one of the main drawbacks of a purely analog device. Comparatively speaking, the range of precision on an analog computer is limited, whereas the precision with a digital computer is much greater. By incorporating  the components that allow the digital computer to go beyond the three to four digits of precision that are common with an analog equipment, hybrid computing makes it possible to handle equations much more rapidly than the digital option alone. In other words, hybrid computing offers both speed and precision, thus eliminating the need for the user to settle for one or the other.
The value of a hybrid computer is readily seen where there is a need to manage equations in a real time fashion. Whereas a strictly analog device would provide quick returns that were not entirely precise, and a digital device would provide more precise responses that would take longer to calculate, the hybrid approach makes it possible to obtain answers now rather than later. At the same time, those answers are more detailed and thus more useful than the fast answers provided by the analog equipment.


Following are some of the other important types of computers.

Mainframe Computers:
A mainframe (also known as "big iron") is a high-performance computer used for large-scale computing purposes that require greater availability and security than a smaller-scale machine can offer. Historically, mainframes have been associated with centralized rather than distributed computing, although that distinction is blurring as smaller computers become more powerful and mainframes  …
Large organizations use mainframes for highly critical applications such as bulk data processing and ERP. Most of the mainframe computers have the capacities to host multiple operating systems and operate as a number of virtual machines and can thus substitute for several small servers.
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Largest data processing system employed in controlling very complex industrial processes, crunching extremely large numbers at extremely high speeds, storing massive amounts  of data, generating life-like animation, processing millions of real-time transactions, and serving thousands of simultaneous users. Mainframes use propritary operationg systems, most of which are based on unix, and a growing number on Linux. Over the years they have evolved from hall-sized dinosaurs to fully IP-networked machines that are extremely competitive and cost effective platforms for e-commerce development and hosting. According to a year 2002 estiate "70% of the world's data is on the mainframes, and 85 percent of all business transactions are still processed on mainframes."
Microcomputers:
"Microcomputer" is an antiquated term that refers to a computer that uses a microprocessor (IC) for its Central Processing Unit, rather than vacuum tubes or bipolar junction transistors, which were commonplace before the microprocessor. In addition, a microcomputer should be small enough to fit on a desk, as microprocessor-based computer larger than that are generally called minicomputer instead. Microprocessor-based computers are the backbone of the modern computer era, often considered "third generation " computers in contrast to the first and second generation of vacuum tubes and bipolar junction transistors. Today, almost all computers are microcomputers.
Microcomputers, or PC's as they are often called, are abundant on our desks, tables, offices, suitcases, everywhere.
This is the most visible form of computers in the present world and comes in all forms and breeds.
There are many generations of particular design and technical specifications from the start of this particular design.
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A computer with a microprocessor and its central processing unit is known as a microcomputer. They do not occupy space as much as mainframes. When supplemented with a keyboard and a mouse, microcomputers can be called as personal computers. A monitor, a keyboard and other similar input output devices, computer memory in the form of RAM and a power supply unit come packaged in a microcomputer. These computers can fit on desks or tables and serve as the best choices for single-user tasks.

Desktops:
A desktop computer is a personal computer (PC) in a form intended for regular use at a single location, as opposed to a mobile laptop or portable computer. Prior to the widespread use of microprocessors, a computer that could fit on a desk was considered remarkably small. Desktop computers come in a variety of types ranging from large vertical tower cases tosmall form factor models that can be tucked behind an LCD monitor. "Desktop" can also indicate a horizontally-oriented computer case usually intended to have the display screen placed on top to save space on the desktop. Most modern desktop computers have separate screens and keyboards. Tower cases are desktop cases in the earlier sense, though not in the latter. Cases intended for home theater PC systems are usually considered to be desktop cases in both senses, regardless of orientation and placement. 
The term is used mainly to distinguish this type of PC from portable computer and laptops , but also to distinguish other types of computer like the PDA, server or mainframe.
Desktops are currently the cheapest and most common computers, and are frequently used by businesses, schools, households and other organizations.
Nearly all modern desktop computers are modular, meaning that the components can easily be replaced or upgraded.
A desktop computer can also refer to a computer who'se case is oriented horizontally. Such cases are called Desktops as opposed to Towers.
Your computer's desktop is much like a physical desktop. You probably keep a number of commonly used items on your desk such as pens, papers, folders, and other items. Your computer's desktop serves the same purpose -- to give you easy access to items on your hard drive. It is common to store frequently used files, folders, and programs on your desktop. This allows you to access the items quickly instead of digging through the directories on your hard drive each time you want to open them. 
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A desktop is intended to be used on a single location. The spare parts of a desktop computer are readily available at relative lower costs. Power consumption is not as critical as that in laptops. Desktops are widely popular for daily use in workplaces and households.

Laptops:

A laptop computer, usually called a notebook computer by manufacturers, is a battery- or AC-powered personal computer generally smaller than a briefcase that can easily be transported and conveniently used in temporary spaces such as on airplanes, in libraries, temporary offices, and at meetings. A laptop typically weighs less than 5 pounds and is 3 inches or less in thickness. Among the best-known makers of laptop computers are IBM, Apple, Compaq, Dell, and Toshiba.

Portable and compact personal computer with the same capabilites as a desktop computer. Laptop computers have an L-shape design and the screen can be lowered and closed to allow for easy transporation of the machine. The primary features that attracts users to laptops over desktops is their portability. Laptop computers provide users the ability  to run the machine using an internal battery or an outside power adaptor. Laptops have dramatically decreased in size since their introduction in 1979. Laptops are usually more  expensive than standard desktops and do not have the same life-span as fixed personal computers. While portable computer used to be significantly slower and less capable than desktop computer, advances in manufacturing technology have enable laptop to perform nearl as well as their desktop counterparts. In fact, high-end laptops often perform better than low or even mid-range desktop system. Most laptops also include several I/O ports, such as USB ports, that allow standard keyboards and mice to be used with the laptop. Modern laptops often include a wireless networking adapter as well, allowing users to access the Internet without requiring any wires
Laptops usually come with displays that use thin-screen technology. The thin film transistor or active matrix screen is brighter and views better at different angles than the STN or dual-scan screen. Laptops use several different approaches for integrating a mouse into the keyboard, including the touchpad the trackball, and the pointing stick. A serial port also allows a regular mouse to be attached. The PC card is insertable hardware for adding a modem or network interface card to a laptop.CD-ROM and digital versatile disc drives may be built-in or attachable.  
While laptops can be powerful and convenient, the convenience often comes at a price. Most laptops cost several hundred dollars more than a similarly equipped desktop model with a monitor, keyboard, and mouse. Furthermore, working long hours on a laptop with a small screen and keyboard may be more fatiguing than working on a desktop system. Therefore, if portability is not a requirement for your computer, you may find better value in a desktop model.
Laptops are capable of many of the same tasks that desktop computers perform, although they are typically less powerful. Laptops contain components that are similar to those in their desktop counterparts and perform the same functions but are miniaturized and optimized for mobile use and efficient power consumption. Laptops usually have LCD displays and smaller SO-DIMM chips for their RAM In addition to a built-in keyboard, they may utilize a touchpad  (also known as a trackpad) or a pointing stick for input, though an external mouse or keyboard can usually be attached. 
  
Personal Digital Assistants (PDAs):

A Personal Digital Assistant (PDA) is a handheld device designed to facilitate organizational ability from a mobile platform. While the original PDAs were somewhat limited to keeping address, phone, calendar, and task lists, today’s PDA can function as a cellular phone, fax, provide Internet connectivity, and much more. There are many different types of PDAs, but most models work with either palmtop software or a special version of Microsoft Windows called Windows Mobile. All models can interface with a laptop or desktop system, though optional accessories may be required. Synchronization between computer and PDA is one of the most popular features of this digital device.  
It is a handheld computer and popularly known as a palmtop. It has a touch screen and a memory card for storage of data. PDAs can also be effectively used as portable audio players, web browsers and smart phones. Most of them can access the Internet by means of Bluetooth or Wi-Fi communication.
A PDA might also incorporate cellular phone functionality and wireless local area network (LAN) capability. Connect to the Internet to check email, send messages, or watch the stock market. With flash card capability, a PDA can store, access, and transfer virtually any kind of data, including maps, spresdsheets, presentations, and dockets.
PDAs range in price from about 100 US Dollars (USD) to 500 USD or more. In general, the more expensive the PDA, the more features it incorporates. Some models have permanent rechargeable batteries, while others use replaceable batteries. Display type and size also play into price.  

 Minicomputers:
In terms of size and processing capacity, minicomputers lie in between mainframes and microcomputers. Minicomputers are also called mid-range systems or workstations. The term began to be popularly used in the 1960s to refer to relatively smaller third generation computers. They took up the space that would be needed for a refrigerator or two and used transistor and core memory technologies. The 12-bit PDP-8 minicomputer of the Digital Equipment Corporation was the first successful minicomputer.
A midsized computer. In size and power, minicomputers lie between wotkstations and mainframes. 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 amultiprocessing system capable of supporting from 4 to about 200 users simultaneously.

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A minicomputer, a term no longer much used, is acomputer of a size intermediate between a microcomputer  and a mainframe. Typically, minicomputers have been stand-alone computers (computer systems with attached terminals and other devices) sold to small and mid-size businesses for general business applications and to large enterprises for department-level operations. In recent years, the minicomputer has evolved into the "mid-range server" and is part of a network. IBM's AS.400e is a good example.
  
Features

  • A mini computer includes many of the same components found in a traditionally sized desktop tower, such as standard processors, memory and optical drives, but placed on a smaller motherboard. Due to space constraints, a mini computer may sacrifice features such as extra expansion slots, more robust power sources or more advanced cooling methods.

    • Types

  • As of 2009, there are several types of mini computers available to consumers.
    The small form PC is a miniaturized version of the standard desktop PC, utilizing standard components on a smaller motherboard, typically in a cube-shaped case with two expansion slots. It was originally referred to as the "shuttle form factor," which referred to the computer manufacturer Shuttle, but it was renamed to "small form factor" to include other makers with similarly designed small computers.
    Nettop computers are extremely small, lightweight computers. They are commonly used for basic computing functions such as Web browsing, media viewing and document creation. Unlike the cubical PCs, nettop computers typically have few, if any, expansion slots.

    Home theatre PCs are mini computers built specifically to act as a home entertainment system. These mini PCs often include larger hard drives to store media-related data as well as TV tuner cards and remote control functions. HTPC cases are usually designed to lay on its side and emulate the look of DVRs and other side-laying home theater equipment.

    • Advantages

  • Mini computers are prized for their portability and have become a mainstay at events such as LAN gaming parties. With their smaller footprint, better aesthetics and quiet operation, mini computers are a popular choice for living room or media room applications. Smaller computers are also less expensive than their traditionally sized counterparts and use less electricity.

    • Disadvantages

  • Smaller computers, particularly nettops, are sometimes believed to be less powerful than full-sized desktop computers, though the validity of this criticism is dependent on what type of processor is used in the device. Though mini computers are more portable, they still require an external monitor, keyboard and mouse, making them more cumbersome than laptops. The smaller size of a mini computer also reduces or eliminates expansion slots, making it less ideal for a user who requires multiple drive bays to accommodate hardware expansion.

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    Supercomputers:
    As the name implies, a supercomputer is no ordinary computer. It is a high performance computing machine designed to have extremely fast processing speeds. Supercomputers have various applications, such as performing complex scientific calculations, modeling simulations, and rendering large amounts of 3D graphics. They may also be built to simply showcase the leading edge of computing technology.
    The highly calculation-intensive tasks can be effectively performed by means of supercomputers. Quantum physics, mechanics, weather forecasting, molecular theory are best studied by means of supercomputers. Their ability of parallel processing and their well-designed memory hierarchy give the supercomputers, large transaction processing powers
    The fastest type of computer. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum exploration. 
    Extremely fast data processing-oriented computer whose number crunching power is (presently) measured in hundreds of billions of floating point operations. Supercomputers rely on parallel-processing technology and can use only a few but very complex programs in modeling economy behaviour, nuclear reactions, meteorological and neurological phenomenon, etc. First supercomputer (Cray-1) was made in 1976 by the US engineer Roger Cray (1925-1996).
    If you are hoping to have a supercomputer on your desk, you may be out of luck, Supercomputer are typically several times the size of a typical desktop computer ad require far more power. A supercomputer may also consist of a series of computer, which may fill an entire room. Examples of single machine supercomputers include the early Cray-1 and Cray X-MP systen developed by Cray Research as well as the more recent Blue Gene and Roadrunner system developed by IBM System X is an example of a multi-system supercomputer, which was developed by virginia tech and is comprised of 1,100 Apple Xserve G5s.
     
    Wearable Computers:
     
      A record-setting step in the evolution of computers was the creation of wearable computers. These computers can be worn on the body and are often used in the study of behavior modeling and human health. Military and health professionals have incorporated wearable computers into their daily routine, as a part of such studies. When the users’ hands and sensory organs are engaged in other activities, wearable computers are of great help in tracking human actions. Wearable computers are consistently in operation as they do not have to be turned on and off and are constantly interacting with the user.
     
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