Acronym

To understand USB better it may be instructive to understand the acronym - which stands for Universal Serial Bus. The words Serial and Bus are crucial.

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Bus reminds you that, though we seem to use USB for data transfer between a computer and an external device much like a serial cable, it is much more than that. To understand the difference, consider what is required to get a serial connection to work on a computer. All that is needed, is a driver for the serial port installed and that would make our serial port functional. We are not concerned about the device that is hooked up at the other end of the serial cable. With the driver installed, the only other utility that maybe required is a serial client application like Hyperterm (if you are using Windows) or Minicom (if you running some flavor of Unix/Linux). The point is that you are only concerned about your end of things. But USB is a bus, like a PCI bus. Since the bus is part of the computer's datapath, it follows that all devices connected the USB cable, by virtue of being 'on the bus', are part of the computer. So, apart from being interested in just putting the bits on the wire - as was the case with the serial link - now we are also concerned about the devices on the other end.

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Serial tells us that data transmission on the wire is serial (as opposed to parallel)- one bit at a time

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Universal clarifies that the standard is portable across devices and platforms