A computer system is a combination of software programs and hardware components. While the structure of the computer system is made of the hardware components, the behavior of the system is determined by the software. Modern computer systems that we use today are digital computers, which are highly accurate and versatile.
Digital computer systems can be categorized into general purpose systems, which form a majority of the computers we use in our say-to-day lives. However, there are also a few special purpose computers that are designed for use in certain fields only. Super computers, mainframes, and micro computers can be considered as general purpose systems that can perform a number of functions and handle several applications at once.
Mainframe systems are large and powerful digital computers with the capacity to process a huge amount of data, and are mostly used by large companies for storing and processing the data they use. Super computers are much larger than mainframes and are generally used for sophisticated research and analysis of scientific, technical or financial data.
Micro computers are the most commonly used computer systems today. Desktops, laptops, tablets and PDA (personal digital assistant) or palm-tops are examples of micro computers. While most of the desktops and laptops have the same features and performing abilities, a number of people today prefer laptops as they are portable and occupy very little space.
However, increasing number of people are turning to the much smaller tablet computer systems or PDAs, which are the size of a big book and have the same features of a desktop or a laptop, except that they can be operated without a keyboard or a mouse. | 
