What is USB?

Last year, someone I know updated his desktop PC. Once we begin to connect all the peripherals such as the keyboard and mouse we noticed something was missing: the serial ports. The only ports included in the desktop were USB ports.

In this post I will provide a brief overview of USB, provide a brief history and discuss what exactly a USB port is used for.

Brief History

USB Logo

Since the inception of the personal computer up until a few years ago, external devices usually connected to a PC through one of two ports: parallel and serial ports. Such things as printers and scanners would connect to the parallel port of a computer that allowed for faster data transfers than the serial ports. Keyboards and mice connected to the serial ports.

As new devices came about, and the amount of data that needed to be transferred it was obvious that the parallel and serial ports would quickly become insufficient. In 1995 a specification for a new serial bus was introduced called USB.

USB is an acronym for Universal Serial Bus. It provides a standard method of connecting external devices to a computer using a standardized socket, and supports plug-and-play that allows devices to be connected and disconnected without rebooting the machine. The USB Implementers Forum (USB-IF) standardizes and designs USB.

In September 1998, USB 1.1 was introduced to help correct adoption problems from the earlier USB versions. The USB 2.0 specification was introduced in 2000 and ratified by the USB-IF in 2001. Version 2.0 increases the transfer speed of USB as well as provides backward-compatibility to the previous versions. This means you can use USB 1.0 and USB 1.1 devices in a USB 2.0 port.

The current version on the market at this time is USB 2.0

The image below shows the USB icon that you will see on many USB cables and devices.

USB Icon

Speed of USB

As with anything in computers, the data transfer rates of USB have increased. The following table shows the transfer rates of the USB versions:

USB VersionSpeed
1.0 and 1.1Low-Speed: 1.5 Mbits/sec
Full-Speed: 12 Mbit/sec
2.0Hi-Speed: 480 Mbit/sec

A new specification for USB 3.0 is planned to be released in 2008 with commercial products expected in 2009 or 2010. The speed of this new version is to reach roughly 5.0 Gbit/sec. As with other versions, it will be backwards-compatible with previous versions.

Using the USB Port

Now that I have provided a brief explanation of what USB is, let’s talk about connecting a device to the port. To connect a device, follow these steps:

  1. If you haven’t attached the device before, then first install the device driver that come included on the CD-ROM that came with the device. This should be done first because one you plug in the device, Windows will detect it and try to load the drivers. If it can’t find any, then you will be prompted to insert the disc with the drivers.
  2. Once the drivers are installed, you can now connect the device. Windows should now detect the device, find the drivers, and then load them. Once the drivers are loaded the device should begin to work. If it doesn’t try re-installing the drivers.

If you have an old printer that uses the parallel port instead of a USB port, you can buy a parallel-to-USB cable that allows you to connect your printer to the USB port.

For older serial mice and keyboards, you can also buy a serial-to-USB cable. There is also a y-cable available that allows you to connect both the mouse and keyboard to one USB port.

If you have more devices than available ports, you can do two things:

  1. Buy a USB hub, which is an external device that contains several USB ports and plugs into a single USB port on your computer.
  2. Buy a PCI card that plugs into a PCI slot in your computer. These cards also contain multiple USB ports. Some cards may even contain both USB and Firewire, which is another type of fast connection port mainly used with digital videos.


I briefly mentioned above about Firewire ports. I have not touched on those types of ports in this post as I will be writing about them in the future.


For many years parallel and serial ports were the ports used to connect external devices to a desktop computer. In 1995 a new standard called USB was introduced and has now become the standard, which most devices use to connect to a computer. With newer USB versions, the data transfer speeds have increased, while providing backwards compatibility with previous versions.

Connect a USB device to your computer is really easy to do: simply install the drivers and then connect the device. There are also cables that allow you to connect older parallel and serial devices to USB ports. If you have more devices than USB ports, you can always connect a USB hub or PCI card that contain several more USB ports.

Follow Me