A system consist of hardware device and operating system on which application, process, and program runs is a computer platform. If we define a term platform, is a group of technologies on which platform is based upon on the other application are developed. It include certain hardware architecture, run time libraries and operating system.
Example: A desktop computer with Microsoft window install on it. This example give a combination of hardware and operating system in which desktop is a hardware device and window is operating system. So as operating system act as an interface between application and computer and also between user and computer. So in order to perform some functionality you need to combine a hardware and operating system to make a usable computer platform.
This type is primarily used by large organization for various application including bulk data, process control, industry and consumer statics and son on. The term referred to as the large cabinets which is called main frames. It was developed first in 1950s and continued to evolve till now and today also in use. It is optimized for computational speed and handle very high volume data. Speed is expressed in MIPS.
Personal computer is also known as microcomputer. It is relatively small as computer to other types and not so expensive, especially designed for a single user. As the term we also used microprocessor, so they are based on microprocessor technology which enables to put an entire CPU on one chip. This used at home is for playing games. Business persons also used to word processing, accounting, desktop publishing, database management and so on.
PC first comes in 1970s which is one of the most popular personal computer. In 1977s Apple II introduced first Apple computer. During the 1970s and 1980s, new model and operating systems seemed to existence. After that in 1981, IBM entered fray which is first personal computer known by IBM PC.
This type of computer platform is smaller is size but posses most of the features and capabilities of a large computer. Fill space between the microcomputer and the mainframe computer platforms. It always use midrange servers operating business as well as scientific application. But now thesedays term is vanished or you can say merged with server.
Minicomputer was developed by IBM Corporation and comes in mid of 1960s. Used as the mid-range servers so that they can be operated in software application and support great number of users at the same time. It can also contain more than one processor they are supporting multiprocessing and tasking. They are powerful then microcomputers and workstation.