USB main attraction is that it makes adding peripherals to your computer incredibly easy. It enables you to connect peripherals to the outside of the computer so you don’t have to open your PC.

Introduced in 1995, the USB standard was developed by industry leaders including IBM, Intel, DEC, Microsoft, and Compaq. Today, PCs and peripherals feature at least one USB port. Peripherals include everything from printers to cameras. Windows 2000, Windows XP, MAC OS, Redhat Linux, and higher support USB.

A USB peripheral simply plugs right into the port and works. USB devices are completely host-swappable. USB configuration happens automatically, so built-in USB means you don’t have to fiddle with drivers and software when adding most peripherals. USB host controllers automatically detect when peripherals are connected to or disconnected from a port. The controllers manage peripheral and allocate the right electrical power to each one.

USB uses a tiered star topology, meaning that USB devices called hubs can serve as connection ports for other USB devices. Only one device needs to be plugged into your PC. A single USB port can support up to 127 devices.

USB 1.1, the original USB standard, has two data rates: 12Mbps for devices such as disk drives that need high-speed throughput and 1.5 Mbps for devices like joysticks that use much less bandwidth.

In 2002, a newer specification, USB2.0, Hi-Speed USB2.0 gained wide acceptance in the industry. It increases the speed of the peripheral-to-PC connection from 12Mbps to 480 Mbps, or 40 times faster.

This increase n bandwidth enhances the use of external peripherals that require high throughput, such as CD/DVD burners, scanners, digital cameras, iPod, video equipment, and more. USB 2.0 also supports demanding applications where multiple high-speed devices run simultaneously, such as Web publishing. A USB 2.0 host works with both USB2.0 and USB 1.1 peripherals.

A newer USB standard, USB On-The-Go, enables portable devices, such as PDAs, digital music player, and mobile phones, to connect to each other without the need for a PC host.

 

 usb connectors

 

There are four types of USB connectors: Type A, Type B, the Mini A, and the Mini B.

USB 1.1 specifies Type A and Type B. USB 2.0 specific Type A, Type B, and the Mini B. The Mini A connector was developed as part of the USB OTG specification and is used for smaller peripherals, such as cell phones and PDAs.