Answer
This question is far too broad:
In chip architectures: There are several in current use, but there are 3 that are most common. Intel's x86 and AMD's x64 are used in almost all modern PCs. There are IBM's PowerPC chips such as the ones in use in old Macintoshes, Playstations and other consoles. Then there are ARM processors used on mobile devices such as the iPhone and iPod Touch, and most smartphones and handhelds.
In hardware configurations: There are almost unlimited combinations of hardware that would work together.
In basic designs: There are desktops, servers, integrated machines, notebooks, tablet computers and subnotebooks and miscellaneous devices such as .
In brands: There are around 200 main brands that sell computers, though they mainly buy parts from other manufacturers, assemble them and install an poerating system on them.
Minicomputer, Laptop... and others!!!
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