MICROCOMPUTERS A microcomputer is a small, relatively inexpensive computer with a microprocessor as its central processing unit (CPU). It includes a microprocessor, memory, and input/output (I/O) facilities. Microcomputers became popular in the 1970s and 80s with the advent of increasingly powerful microprocessors. microcomputer contains a microprocessor (a central processing unit on a microchip ),memory in the form of read-only memory and random access memory , I/O ports and a bus or system of interconnecting wires, housed in a unit that is usually called a motherboard . Monitors, keyboards and other devices for input and output may be integrated or separate. Computer memory in the form of RAM, and at least one other less volatile, memory storage device are usually combined with the CPU on a system bus in one unit. Other devices that make up a complete microcomputer system include batteries, a power supply unit, a keyboard and various input/output devices used to convey information to and from a human operator (printers, monitors, human interface devices). Microcomputers are designed to serve only one user at a time, although they can often be modified with software or hardware to concurrently serve more than one user. Microcomputers fit well on or under desks or tables, so that they are within easy access of users. Bigger computers like minicomputers, mainframes, and supercomputers take up large cabinets or even dedicated rooms. A microcomputer comes equipped with at least one type of data storage, usually RAM. Although some microcomputers (particularly early 8-bit home micros) perform tasks using RAM alone, some form of secondary storage is normally desirable. In the early days of home micros, this was often a data cassette deck (in many cases as an external unit). Later, secondary storage (particularly in the form of floppy disk and hard disk drives) were built into the microcomputer case. Desktop computers, laptops, personal digital assistant (PDA), tablets & smartphones are all types of microcomputers. The micro-computers are widely used & the fastest growing computers. These computers are the cheapest among the other three types of computers. The Micro- computers are specially designed for general usage like entertainment, education and work purposes. Well known manufacturers of Micro-computer are Dell, Apple, Samsung, Sony & Toshiba. Desktop computers, Gaming consoles, Sound & Navigation system of a car, Netbooks, Notebooks, PDA’s, Tablet PC’s, Smartphones, Calculators are all type of Microcomputers. Personal Computer or PC – A PC is a computer that is used by someone for his personal use. It is a complete system in itself and its convenient size, price and simple functions make it easy for the end-user to work on it without any intervention from computer operators. Desktop – Any PC that is designed to be placed on a desk and not for portability is called a desktop. Such computers are kept in a somewhat permanent location and can be a little bulky. They usually have more power and storage compared to their movable counterparts. Laptop or Notebook – A PC that can be moved around is called a laptop. It gets its name from the fact that you can keep it on your lap and use it. It is also called a notebook because you can carry the battery-operated device to classes or meetings conveniently and store any notes or information in it. It integrates the monitor, keyboard, pointing device, CPU, memory and hard drive in one system. Netbook – This is similar to a laptop, the only difference being that it is smaller in size, which makes it even more portable. It is also less expensive and performs the basic functions, but its internal parts are not as powerful as a desktop or laptop. Workstation – This computer is a desktop which is larger, consists of a more powerful processor, greater memory space and extra ability to do specific kind of work. Such a computer is used by programmers, game developers, video or sound editors and graphic designers. PDA – A Personal Digital Assistant is a small, highly integrated computer usually using flash memory for storage instead of a hard drive. It uses touchscreen technology and doesn’t have a keyboard. Those which use a digital pen for input are called handheld computers. It is light, portable, has good battery life and fits within your palm, because of which it is also called a palmtop. Popular computers include CyberPower Zeus Mini - Asus Chromebox M004U - Apple Mac Pro (2013) MINICOMPUTERS Minicomputers are used by small businesses & firms. These are small machines and can be accommodated on a disk with not as processing and data storage capabilities as super-computers & Mainframes. These computers are not designed for a single user. Individual departments of a large company or organizations use Mini-computers for specific purposes. For example, a production department can use Mini-computers for monitoring certain production process. Minicomputers (colloquially, minis) are a class of multi-user computers that lie in the middle range of the computing spectrum, in between the smallest multi-user systems (mainframe computers) and the largest single-user systems (microcomputers or personal computers). The term superminicomputer or super mini was used to distinguish more powerful minicomputers that approached mainframes in capability. Super minis were usually 32-bit at a time when most minicomputers were 16-bit. The contemporary term for minicomputer is midrange computer, such as the higher-end SPARC, POWER and Itanium-based systems from Oracle Corporation, IBM and Hewlett-Packard. A minicomputer, or colloquially mini, is a class of smaller computers that evolved in the mid-1960s and sold for much less than mainframe and mid-size computers from IBM and its direct competitors.. Minis were designed for control, instrumentation, human interaction, and communication switching as distinct from calculation and record keeping. Many were sold indirectly to Original Equipment Manufacturers (OEMs) for final end use application. During the two decade lifetime of the minicomputer class (1965-1985), almost 100 companies formed and only a half dozen remained. When single-chip CPUs appeared, beginning with the Intel 4004 in 1971, the term "minicomputer" came to mean a machine that lies in the middle range of the computing spectrum, in between the smallest mainframe computers and the microcomputers. Examples include the higher- end SPARC, Power Architectureand Itanium-based systems from Oracle, IBM and Hewlett- Packard. A variety of companies emerged that built turnkey systems around minicomputers with specialized software and, in many cases, custom peripherals that addressed specialized problems such as computer aided design, computer aided manufacturing, process control, manufacturing resource planning, and so on. Many if not most minicomputers were sold through these original equipment manufacturers and value-added resellers.Several pioneering computer companies first built minicomputers, such as DEC, Data General, and Hewlett-Packard (HP) (who now refers to its HP3000 minicomputers as "servers" rather than "minicomputers"). And although today's PCs and servers are clearly microcomputers physically, architecturally their CPUs and operating systems have evolved largely by integrating features from minicomputers. MAINFRAMES Although Mainframes are not as powerful as supercomputers, but certainly they are quite expensive nonetheless, and many large firms & government organizations uses Mainframes to run their business operations. The Mainframe computers can be accommodated in large air- conditioned rooms because of its size. Super-computers are the fastest computers with large data storage capacity, Mainframes can also process & store large amount of data. Banks educational institutions & insurance companies use mainframe computers to store data about their customers, students & insurance policy holders. Popular Mainframe computers: Fujitsu’s ICL VME Hitachi’s Z800 The term mainframe computer was created to distinguish the traditional, large, institutional computer intended to service multiple users from the smaller, single user machines. These computers are capable of handling and processing very large amounts of data quickly. Mainframe computers are used in large institutions such as government, banks and large corporations. They are measured in MIPS (million instructions per second) and respond to up to 100s of millions of users at a time. Mainframe computers are used by large companies and organizations to perform critical tasks that involve bulk data processing like transaction processing, census information, statistical data and so on. They consist of extensive input and output facilities, are very stable and dependable and handle millions of transactions every day. Mainframe computers are used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning and transaction processing. The term originally referred to the large cabinets called "main frames" that housed the central processing unit and main memory of early computers. Later, the term was used to distinguish high-end commercial machines from less powerful units. Most large-scale computer system architectures were established in the 1960s, but continue to evolve. Modern mainframe design is generally less defined by single-task computational speed (typically defined as MIPS rate or FLOPS in the case of floating point calculations),