USB

Last updated: December 12, 2009.

You can shake hands with someone you meet because their hand is roughly the same size and shape as yours. But just try shaking hands with a cow, a dog, or a fish. We can get along with other people because humans all broadly work the same way, think in similar ways, and talk the same language. Thankfully, the same is also now true of our computers and their peripherals (gadgets like inkjet printers, webcams, and flash memory sticks).

But that wasn't always the case. A few years ago, computers and peripherals used a mind-boggling collection of different connectors for linking to one another. It was hard (sometimes impossible) to use a certain computer with a particular printer and, if you bought a new printer, it was often touch-and-go whether it would work with your old computer. These days, virtually all computers and peripherals use a standard way of connecting together called USB. which stands for "universal serial bus." What's it all about—and how does it work?

Photo: Ever wondered what's inside a USB flash memory stick? Now you know!

The basic idea of USB

Ten or twenty years ago, if you'd bought a new computer, you'd have found a whole collection of different connecting sockets or ports built into its case. There were serial ports, parallel ports, infra-red ports (for connecting things wirelessly), and all kinds of other ports. Most people had no idea what half their ports were for or what to do with them.

Photo: Before USB: A selection of old-style serial and parallel computer connectors. They had lots of tiny copper or gold connecting pins that were easily bent or broken if you pulled or pushed them too hard.

If you wanted to use a new peripheral, such as a webcam or printer, you had to go through a lengthy installation process. You had to install a file called a driver (which told your computer what the peripheral was and how it worked), which usually took ages. Quite you often had to reboot the computer when you were done, so installing a peripheral was incredibly slow and disruptive.

In those days, the computer makers didn't really care about things working together. Acme Computers wanted you to buy their Acme printers and Acme scanners, not Bronco printers and Bronco scanners. So every manufacturer made sure its own range of products worked together but didn't really give a hoot about anyone else's. Eventually, when it became clear that users wanted to be able to use whatever peripherals they liked, the computer makers got together and agreed they'd stop being so selfish and greedy and all do things the same way. That's how USB became what's called a standard: an agreement between manufacturers to behave sensibly and cooperate.

With the development of USB, everything changed. Pretty much every personal computer now has two or more USB sockets built into its case and every peripheral has a USB plug on the end of it. You can plug any USB device into any USB socket with a reasonable expectation that it will work. Even better, your computer should detect the device, figure out what it is, and try to install a driver automatically. You don't have to wait long and you don't have to reboot your computer. When you're finished using one USB device, you can just whip it out and plug in another one. Your computer will automatically detect what's going on and keep track of what's plugged into it without you having to worry in the slightest. In other words, you can "plug and play" to your heart's content.

Photo: A selection of USB adapters. Use these to convert old keyboards and mice with PS/2 plugs to work with new-style USB sockets.

USB also supplies power

USB has some other neat features too. The old-style serial connectors you found on computers were simply for sending data (information) back and forth. But USB also has a built-in 5-volt (approximately) power wire, so it can drive most low-power peripherals without the need for an external power supply. When you plug an external hard-drive into the USB socket of your computer, the computer is sending electric power  to drive the electric motor and circuitry in the hard drive as well as sending data to and from the drive. That means you don't have to have a bulky power supply and transformer attached to the drive. So USB makes computers much more neat and compact, which is particularly good news for laptop users.

Simply the best

Photo: USB connectors are a cinch to plug and unplug.

But the greatest virtue of USB is its sheer simplicity: even your grannie can plug and unplug her webcam without studying for a PhD in computer science. The plugs are really easy to take in and out (unlike old-style parallel printer plugs, which you had to screw to the back of your computer to stop them falling out!) with hardly any force. You can't possibly put them in the wrong way round and cause damage. Unlike old-style connectors, they don't have lots of fragile pins to get bent up and damaged each time you take them in and out. They're very robust—so you can plug and unplug them zillions of times.

There is one thing to careful about. USB sockets on computers are soldered directly to the computer's main circuit board (often quite weakly) and if you press them too hard you can break the connections, which stops them from working. So be slow and gentle when you're taking plugs in and out. Don't push them in hard or yank them back out again.