Based on performance, size, cost and capacity, the digital computers are classified into four different types : Super computers, Mainframe computers, Mini computers and Micro computers.
The mightiest computers but at the same time, the most expensive ones are known as super computers. Super computers process billions of instructions per second. In other words, super computers are the computers normally used to solve intensive numerical computations. Examples of such applications are stock analysis, special effects for movies, weather forecasting and even sophisticated artworks.
Mainframe Computers Mainframe computers are capable of processing data at very high speeds – hundreds of million instructions per second. They are large in size. These systems are also expensive. They are used to process large amount of data quickly. Some of the obvious customers are banks, airlines and railway reservation systems, aerospace companies doing complex aircraft design, etc.
Mini Computers The mini computers were developed with the objective of bringing out low cost computers. They are lower to mainframe computers, in terms of speed and storage capacity. Some of the hardware features available in mainframes were not included in the mini computer hardware in order to reduce the cost. Some features which were handled by hardware in mainframe computers were done by software in mini computers. Hence the performance of mini computer is less than that of the mainframe. However, the mini computer market has diminished somewhat as buyers have moved towards less expensive but increasingly powerful personal computers.
Micro Computers The invention of microprocessor (single chip CPU) gave birth to the micro computers. They are several times cheaper than mini computers.
The micro computers are further classified into workstation, personal computers, laptop computers and still smaller computers. Although the equipment may vary from the simplest computer to the most powerful, the major functional units of the computer system remain the same : input, processing, storage and output. Workstations Workstations are also desktop machines mainly used for intensive graphical applications. They have more processor speed than that of personal computers.
Workstations use sophisticated display screens featuring high resolution colour graphics. Workstations are used for executing numeric and graphic intensive applications such as Computer Aided Design (CAD), simulation of complex systems and visualizing the results of simulation.
Today the personal computers are the most popular computer systems simply called PCs. These desktop computers are also known as home computers. They are usually easier to use and more affordable than workstations. They are self-contained desktop computers intended for an individual user. Most often used for word processing and small database applications.
Laptop computers are portable computers that fit in a briefcase. Laptop computers, also called notebook computers, are wonderfully portable and functional, and popular with travelers who need a computer that can go with them. Getting Smaller Still.
Pen-based computers use a pen like stylus and accept handwritten input directly on a screen. Pen-based computers are also called Personal Digital Assistants )PDA(. Special engineering and hardware design techniques are adopted to make the portable, smaller and light weight computers.