The types of computers range from the Hybrid to the Analog types. The computers you come across in the daily course of your day range from laptops, palmtops and towers, to desktop computers, to name a few. But the very word “computers” reminds one of the desktop computers used in offices or homes. Different categories of computes have been devised in keeping with our varied needs. The Types Of Computers: Analog and Hybrid (classification based on operational principle) • Analog Computers: The analog computer is almost an extinct type of computer these days. It is different from a digital computer in respect that it can perform numerous mathematical operations simultaneously. It is also unique in terms of operation as it utilizes continuous variables for the purpose of mathematical computation. It utilizes mechanical, hydraulic, or electrical energy or operation. • Hybrid computers: These types of computers are, as the name suggests, a combination of both Analog and Digital computers. The Digital computers which work on the principle of binary digit system of “0” and “1” can give very precise results. But the problem is that they are too slow and incapable of large scale mathematical operation. In the hybrid types of computers the Digital counterparts convert the analog signals to perform Robotics and Process control. Apart from this, computers are also categorized on the basis of physical structures and the purpose of their use. Based on Capacity, speed and reliability they can be divided into three categories of computers: 1. The Mainframe Computer – These are computers used by large organizations like meteorological surveys and statistical institutes for performing bulk mathematical computations. They are core computers which are used for desktop functions of over one hundred people simultaneously. 2. The Microcomputer – These are the most frequently used computers better known by the name of “Personal computers”. This is the type of computer meant for public use. Other than Desktop Computer the choice ranges as follows: • Personal Digital Computer • Tablet PC • Towers • Work Stations • Laptops • Hand Held Computer 3. The Mini computer – Mini computers like the mainframe computers are used by business organization. The difference being that it can support the simultaneous working of up to 100 users and is usually maintained in business organizations for the maintenance of accounts and finances. Yet another category of computer is the Super Computers. It is somewhat similar to mainframe computers and is used in economic forecasts and engineering designs. Today life without computers is inconceivable. Usage of different types of computers has made life both smooth and fast paced. Laptop: Laptops or Notebook computers are a type of personal computers which are portable devices. The special feature of laptop computers is that it is far lighter than a Desktop PC. Being a wireless system, you can use it even when there is a power cut or you are away from home where electricity is not available. Laptops or Notebook Computers are different from a desktop computer not only in terms of size and portability but the following factors count for the basic difference: • In laptops, the mouse, keyboard and sound box is integrated with the main system itself. • A notebook computer is not powered by electricity but by a battery. • Nowadays networking features like Intel Centrino mobile Technology is installed within the laptop computers itself. • In most laptops with the exception of a few like Alienware, the internal parts cannot be updated once you have bought the Laptop. • And to say the least it is far more fragile than a Desktop PC. While buying a Laptop computer you need to consider the quality of the portable computer. What accounts for the portability, are the following factors. So make sure to check out that the basic components of the system, that is to say, the Processor, Memory, Mass Storage and Removal components and the peripheral accessories should be designed in such a way that it is • as light and small as possible; • should be powered by a proper battery which must generate minimum heat; • should be accessible by a floppy or a CD. With the market pouring over with companies such as Compaq, Acer, Toshiba, Zenith, Sahara, HCL, Lenovo, Del Inspiration, ASUS, HP computers, Apple Computers, Alienware and many more, you can choose laptops ranging in price anywhere between 29000 ICR to anywhere beyond 1,00,000. Personal: Personal computers or Microcomputers are the most widely used computers which have found application in everyday activity of the modern world. The speed and accuracy of processing of the personal systems account for their high popularity. think of a world where share market trading had to be carried out manually and the times when the fastest means of communication was but for the telephones were the telegrams. Those days are not even past 50 years, yet you cannot imagine life without the aid of personal computers or “PCs” as you abbreviate them. Personal computers remind us mostly of Desktop computers or at the most Laptop computers. But actually Personal computers refer to:- • Desktop computers – Desktop Computers are those Personal computers that one comes across in business institutions, ATM s, Offices, etc. They have the second largest market among all kinds of PCs. They are unportable and long lasting. • Laptop computers – Laptop Computers are a personal system sub-type. As the name goes, it is a portable computer which is usually a light weight PC. The special feature of course, is that it is far lighter than a Desktop PC and being a wireless system, you can use it even when there is a power cut or you are away from home where electricity is not available • Hand held computers or palm tops – Palm tops like laptops are portable personal computers which are even smaller and lighter and can be carried in a pocket. Ideally a palmtop is used for storage of personal information like phone numbers, appointments and the likes. Nowadays with the improvement of technology palmtops come with colored monitors, sound recording facilities, and even provision for access to the Internet. • Tablet Personal Computers – Tablet PCs are also a kind of micro computers. They are mostly used in Graphics work is an electronic device that utilizes digital ink to write or draw directly on the monitor of you PC. • Work Stations – This is slightly different from the regular PC in respect that it has evolved from the mini computers. Originally used for Engineering, Graphics and such other non-personal work or technical work, work station computers were designed for the purpose of singular interaction of computer with one person at a time. The personal computers or Micro computers are manufactured by several multinational companies such as the HP computers, HCL, Del Inspiration, Acer, Toshiba and many more. INPUT DEVICES: A trackball is a pointing device consisting of a ball held by a socket containing sensors to detect a rotation of the ball about two axes—like an upside- down mouse with an exposed protruding ball. The user rolls the ball with the thumb, fingers, or the palm of the hand to move a cursor. Large tracker balls are common on CAD workstations for easy precision. Before the advent of the touchpad, small trackballs were common on portable computers, where there may be no desk space on which to run a mouse. Some small thumbballs clip onto the side of the keyboard and have integral buttons with the same function as mouse buttons. The trackball was invented by Tom Cranston and Fred Longstaff as part of the Royal Canadian Navy's DATAR system in 1952, [1] eleven years before the mouse was invented. This first trackball used a Canadian five-pin bowling ball. The world's first trackball invented by Tom Cranston, Fred Longstaff andKenyon Taylor working on the Royal Canadian Navy's DATAR project in 1952. It used a standard Canadian five-pin bowling ball. When mice still used a mechanical design (with slotted 'chopper' wheels interrupting a beam of light to measure rotation), trackballs had the advantage of being in contact with the user's hand, which is generally cleaner than the desk or mousepad and does not drag lint into the chopper wheels. The late 1990s replacement of mouseballs by direct optical tracking put trackballs at a disadvantage and forced them to retreat into niches where their distinctive merits remained more important. Most trackballs now have direct optical tracking which follows dots on the ball. As with modern mice, most trackballs now have an auxiliary device primarily intended for scrolling. Some have a scroll wheel like most mice, but the most common type is a “scroll ring” which is spun around the ball. Kensington's SlimBlade Trackball similarly tracks the ball itself in three dimensions for scrolling. Three major companies Logitech, A4Tech, and Kensington currently produce trackball, although A4Tech has not released a new model in several years. Microsoft was a major producer, but has since discontinued all of its products. The Microsoft Trackball Explorer continues to be extremely popular (it has no analogous design in production by another company), with used models selling for ~$200 on ebay. A trackball is a computer cursor control device used in many notebook and laptop computers. The trackball is usually located in front of the keyboardtoward the user. Essentially, the trackball is an upside-down mouse that rotates in place within a socket. The user rolls the ball to direct the cursor to the desired place on the screen and can click one of two buttons (identical to mouse buttons) near the trackball to select desktop objects or position the cursor for text entry. IBM's ThinkPad series of notebook computers uses a "pointing stick", called a TrackPoint, that is integrated into the middle of the keyboard keys.