Introduction of Computer PDF

LEBANESE FRENCH UNIVERSITY Information Technology Department Classifications of Computers The classification of computers is based on the following three criteria 1. According to Purpose 2. According to Technology used 3. According to size and Capacity Accordi...

LEBANESE FRENCH UNIVERSITY Information Technology Department Classifications of Computers The classification of computers is based on the following three criteria 1. According to Purpose 2. According to Technology used 3. According to size and Capacity According to Purpose According to the utilization of computers for different uses, computers are of the following two types: 1. General Purpose Computers Computers that follow instructions for general requirements such as sales analysis, financial accounting, invoicing, inventory, management information, etc. are called General-Purpose Computers. Almost all computers used in offices for commercial, educational, and other applications are general-purpose computers. 2. Special Purpose Computers Computers designed from scratch to perform special tasks like scientific applications and research, weather forecasting, space applications, medical diagnostics etc.  According to Technology Used According to the technology used, computers are of the following three types 1. Analog Computers Analog computers are special-purpose computers that represent and store data in continuously varying physical quantities such as current, voltage, or frequency. These computers are programmed to measure physical quantities like pressure, temperature, speed, etc., and to perform computations on these measurements. Analog computers are mainly used for scientific and engineering applications. Some of the examples of analog computers are given below: Thermometer It is a simple analog computer used to measure temperature. In a thermometer, the mercury moves up or down as the temperature varies. Speedometer Car's speedometer is another example of analog computer where the position of the needle on the dial represents the speed of the car. 4 2. Digital Computers: Digital computers are mainly general-purpose computers that represent and store data in discrete quantities or numbers. In these computers, all processing is done in terms of numeric representation (Binary Digits) of data and information. Although the user enters data in decimal or character form, it is converted into binary digits (0 and l). 3. Hybrid Computers: Hybrid computers incorporate the technology of both analog and digital computers. These computers store and process analog signals which have been converted into discrete numbers using analog-to-digital converters. They can also convert the digital numbers into analog signals or physical properties using digital-to- analog converters. Hybrid computers are mainly used in artificial intelligence (robotics) and computer aided manufacturing (e.g. process control). 5  According to Size and Capacity According to the size and memory/storage capacity, computers are of t h e following four types 1. Supercomputer The supercomputer is the biggest and fastest computer, which is mainly designed for complex scientific applications. It has many CPUs (Central Processing Units the main part of the computer) which operate in parallel to make it the fastest computer Some examples of supercomputers are CRAY3, CRAY-XMP-14, NEC500, P ARAM 9000, and P ARAM 10000. -. It is typically used for the following applications: Weather Forecasting Petroleum Exploration and Production Energy Management Defense Nuclear Energy Research Structural Analysis Electronic Design Real-time Animation Medicine 6 2. Mainframe Computer Mainframe computers are very large and fast computers but smaller and slower than supercomputers. These are used in a centralized location where many terminals (input/output devices) are connected with one CPU and thus, allow different users to share the single CPU. They have a very high memory (several hundred Megabytes) and can support thousands of users. They are mainly used for the following applications Railway and Airline Reservations Banking Applications Commercial Applications of Large Industries/Companies Some examples of mainframe computers are IBM 3090, IBM 4381, IBM 4300, and IBM ES-9000. 3. Minicomputer Minicomputers are medium-scale, smaller, and generally slower than mainframe computers. Like mainframes, they have many terminals which are connected to one CPU and can support many users. The cost of a minicomputer is very low as compared to the mainframe. Therefore, it is mainly used in applications where processing can be distributed among several minicomputers rather than using a mainframe computer.Some of examples of minicomputers are PDP-1, IBM AS/400, and DEC Micro VAX. IBM AS/400, which is a minicomputer (computer with performance between a mainframe and minicomputer), is becoming very popular among minicomputer. 7 4. Microcomputer A microcomputer is the smallest digital computer, which uses a microprocessor as its CPU. Microprocessor is a single-chip (Integrated Circuit) CPU. The microcomputer is popularly called a Personal Computer (PC). It can be used both as a stand-alone machine and a terminal in a multi-user environment. Microcomputers are becoming very popular nowadays due to very high processing power and memory. Today, a powerful microcomputer may be used as a Computer – An Introduction substitute for a mini or mainframe computer. Microcomputers are either desktop or portable models. Portable computers can be carried from one place to another. Some of the models are called laptops while others as notebook computers. Notebook computers are smaller, lighter, and costlier than laptops. Desktop computers fit on a desktop and are used widely in offices and homes. 8