List of computer size categories

This list of computer size categories attempts to list commonly used categories of computer by the physical size of the device and its chassis or case, in descending order of size. One generation's "supercomputer" is the next generation's "mainframe", and a "PDA" does not have the same set of functions as a "laptop", but the list still has value, as it provides a ranked categorization of devices. It also ranks some more obscure computer sizes. There are different sizes like-mini computers, microcomputer, mainframe computer and super computer. 
Distinctive marks.
The classes above are not rigid; there are "edge devices" in most of them. For instance, the "subnotebook" category can usually be distinguished from the "PDA" category because a subnotebook has a keyboard and a PDA has not; however, tablet PCs may be larger than subnotebooks (making it seemingly correct to classify them as laptops) and also lack a keyboard, while devices such as the Handspring Treo 600 have something that might charitably be called a keyboard, but are still definitely in the "smartphone" category.
In the higher end of the spectrum, this informal and somewhat humorous rule might help: