A supercomputer is a computer that performs at or near the currently highest operational rate for computers. A supercomputer is typically used for scientific and engineering applications that must handle very large databases or do a great amount of computation.
Mainframes are computers where all the processing is done centrally, and the user terminals are called "dumb terminals" since they only input and output (and do not process).
Mainframes are computers used mainly by large organizations for critical applications, typically bulk data processing such as census. Examples: banks, airlines, insurance companies, and colleges.
It is also known as a Microcomputer. Its physical characteristics and low cost are appealing and useful for its users. Throughout the 1970s and 1980s, home computers were developed for household use, offering some personal productivity, programming and games, while somewhat larger and more expensive systems (although still low-cost compared with minicomputers and mainframes) were aimed for office and small business use.
Portable computer is a personal computer that is designed to be easily transported and relocated, but is larger and less convenient to transport than a notebook computer. The earliest PCs designed for easy transport were called portables. As the size and weight of most portables decreased, they became known as laptop computer and later as notebookcomputer.
PDA (personal digital assistant) is a term for any small mobile hand-held device that
provides computing and information storage and retrieval capabilities for personal or
business use, often for keeping schedule calendars and address book information handy.