CLASSIFICATION OF COMPUTERS!
Based on the technology used for the construction of CPU in the computers, they are classified as Microcomputers, Mini computers, Mainframe computers and Super computers. Based on the interconnection of computers, we can classify them as distributed computers and parallel computers. The computers, which use Microprocessors as their CPU, are called Microcomputers. Today most of the computers are of this category. Based on the mode of use, microcomputers are further classified into Personal computers, Portable computers and Workstations.
Personal Computers (PCs)
Personal computers are computers used by individuals for the purpose of running the stand-alone applications like Word Processing, Spread Sheet etc. Data and applications stored in a PC are not available for sharing by other computer users. To make use of the resources available in a PC, it must be connected to a network.
There are two major manufactures of PCs – IBM and APPLE. The machines made by IBM are called IBM PCs. The PCs made by APPLE are called Apple Macintosh. Other manufacturers of PCs also followed the same specifications and design of IBM PCs for the manufacturing of their PCs. The PCs made by third party vendors are known as IBM compatible PCs.Early PCs designed by IBM had Intel 8088 microprocessors as their CPU. The Operating Systems used by IBM PCs include MS DOS, MS Windows, Windows-NT, UNIX and OS/2. OS/2 is an OS designed specially for IBM PCs.
Apple Macintosh PCs use Apple’s proprietary OS, which was well known for its user friendliness. Apple Macintosh machines started using Motorola 68030 as their microprocessors but later they switched over to Power PC 603 processors.
Portable Computers
Portable computers are smaller in size but more powerful than personal computers. They can be easily carried out by professionals, researchers and entrepreneurs while they are on the road. There are two types of portable computers: Palmtop and Laptop PCs.Palmtop PCs: Palmtop computers can be held in a palm like a mobile phone kit. Palmtop PCs have a small screen display for both input and output. They can accept handwritten inputs given using electronic pen. A Palmtop PC can also be used as a mobile phone, Fax and email machine. Windows-CE is the OS provided by Microsoft for the operation of Palmtop PCs.
Laptop PCs: Laptop computers are also known as Notebook computers, which can be kept on the lap for working with it. A Laptop PC weighs around 2 Kg and can be carried out easily while traveling. Laptop PCs cost more - at least 3 to 4 times the cost of desktop PCs of the same capacity because of the use of miniature components, which consume low power. They can run on batteries as they have been designed to conserve energy. The configuration of a Laptop PC includes a keyboard, flat screen liquid crystal display, and a Pentium or Power PC processor.
Workstation PC
Workstations are more powerful and more expensive than desktop computers. They can operate at higher speeds – about 10 times faster than PCs. They are generally used by scientists, engineers, and other professionals for handling huge volume of data. They are more suitable for numeric and intensive graphic applications.
The configuration of a typical Workstation includes: a color Video Display Unit (19 inch monitors), 256 MB to 1 GB RAM as main memory and a hard disk of 40-80 GB. Workstations normally use RISC processors such as SUN’s ULTRASPARC, HP’s PA 8500 etc. The OS used by Workstations are UNIX, Linux, SUN Solaris and OS-8.
A system called X Windows is used for Workstations to display the status of multiple processes going on during execution. Most workstations have built-in hardware to connect them to a Local Area Network (LAN).
Mini Computers
Minicomputers, also known as mid range computers were first developed as special-purpose mainframe computers. They were introduced for controlling the machines used in manufacturing industry. However, now they are widely used as general-purpose computers. The most popular minicomputer system is VAM, made by Digital Equipment Corporation (DEC).
Mini computers work well for Distributed Computing Environment (DCE), where the processing power is decentralized and distributed across different computers. An example for distributed computer architecture is Client/Server architecture, in which end users can work with their own microcomputers, and at the same time they can also access and share the resources on the server, which usually is a minicomputer.
Mainframe & Super Computers
Mainframe computers are more powerful than workstations. They are much bigger, faster and more expensive than workstations. Mainframes can process several million-program instructions per second. Organizations like insurance companies, banks, airlines and railways make use of Mainframe computers for handling large number of on-line transactions.Mainframes can store several Tera bytes of data and transfer data from disk to main memory at several hundred Megabytes/sec. They normally use proprietary operating systems, which usually provide extensive services such as user accounting, file security and control. There are very few manufacturers of mainframe computers, which include IBM and Hitachi.
Supercomputers are the fastest computers available at any given time. They are normally used to solve problems, which require intensive numerical computations. Examples of such problems are: numerical weather prediction, designing supersonic aircrafts, design of drugs and modeling complex molecules. In order to solve such complex problems, many RISC processors are used in the construction of super computers.
The speed of operation of supercomputers is in terms of nanoseconds and even in Pico seconds. Besides arithmetic speed, supercomputers have a large main memory of around 16 GB and a secondary memory of 1000 GB. The speed of data transfer between the secondary memory and the main memory is at least one tenth of the speed of data transfer between main memory and CPU. Such great speed is achieved in super computers through a mechanism called Parallelism.
