The computer case serves mainly as a way to physically mount and contain all of the actual components inside of a computer, like the motherboard, hard drive, optical drive, floppy disk drive, etc. They typically come bundled with a power supply.
Motherboards come in a range of different form factors. The form factor of a motherboard will determine its physical size, as well as where all the screw-holes are for mounting it, and each form factor will usually have a fixed location for the rear-IO (such as USB sockets) on the motherboard. The most popular current motherboard form-factors are ATX and micro- ATX. Mini-ITX motherboards are sometimes also seen. The larger motherboards will have more room on them for components and expansion cards, for example more slots for components such as RAM, or more PCI slots. For ATX, MicroATX, and MiniITX the same screw-hole layout is used for securing them in place, with larger boards merely having more screw-holes, thus any case or enclosure that can fit a larger motherboard of these will also accept the smaller variations as well. Computer cases will usually only fit up to a certain size of motherboard in them, and will not accept any larger standards.
Computer cases will have certain areas in which fans can be placed. These areas will have screw-holes for a certain fan size or fan sizes, as well as a circle of grill or mesh in the case to allow air to flow through mostly unobstructed. More fan slots can be beneficial for those who want maximum cooling for their PC, however having lots of unused fan slots can impede cooling, as there may be lots of holes for air to be pushed/pulled through, resulting in less air being moved over the critical components to be cooled. This is usually not a problem, however.
PC cases can also have mounting points for radiators. Water cooling radiators are typically
rectangular in shape, as opposed to the square mounting holes of case fans, and their additional
size means many cases will not fit standard watercooling radiator sizes.
Cases that have mounting-holes for watercooling radiators will often be said to have watercooling support
.
PCs often have large quantities of cables inside to transfer data and power between the internal components, and these can get untidy and unsightly if not managed properly. Cable management refers to the practice of securing these cables out of the way such they are unable to move about inside the case, and are neat and tidy. Cable management is not technically necessary, and many people do not bother, however proper cable management has the advantages of allowing cable paths to be easily seen, thus allowing their start/end points to be easily determined, which can help with upgrading or troubleshooting. Cable management also prevents cables from moving about, and can thus prevent them from falling into fans should the case be knocked or moved whilst running, which can damage the fan, as well as preventing cooling of the component if the fan is then unable to run, which can cause further issues.
Cable management usually comes in the form of cutouts in the motherboard tray and other areas of the case through which cables can be passed through, as well as loops or hooks to which cables or groups of cable ties can be cable-tied, Velcro’ed or otherwise attached to. Good cases will also sometimes rubber coat the cable management holes, hooks, or areas to tidy them up more, as well as prevent the cables pulling on the sharper metal of the case.