You can use USB adapters. But USB does not cover as many interfaces as expension slots.
The motherboard.
Expansion ports to the rear.
ports
The processor is to the top and expansion ports to the rear.
Expansion card
Peripheral ports such as COM, USB and serial ports, are input/output interfaces that allow devices to connect to a computer. Expansion slots are sockets on the motherboard where an expansion card is inserted.
One way to add USB ports to a computer you need a USB expansion card that you add to the motherboard. The card usually has multiple USB ports built into them.
Dictionary: expansion - noun The act or process of expanding In this case you are expanding the capability of your motherboard. Though you didn't mention what type of expansion slot. ISA, PCI, PCI-E or AGP? These ports allow you to add more graphics cards, extra communication ports, network ports, flash memory boards, extra sata/scsi/ide controllers.
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Depends on the type of hub you're talking about. A USB expansion hub for example would allow for additional USB ports.
Most cases have the motherboard ports in the back that way you can hide all the cables and keep them away from alot of activity that may disconnect them.I have not seen a PC with front motherboard ports. But i think its better to leave those ports where they are :)
do you mean "motherboard I/O ports"? Eg. USB, PS/2, Serial, Parallel...