The Universal Serial Bus is, quite simply, a way to connect external devices to computers without utilizing the serial and parallel ports which are typically provided at the back of the CPU. The Universal Serial Bus port may be present anywhere on the body of the CPU, and a modern-day CPU can have numerous USB ports, some behind and some out in front.
My own PC has four USB ports at the back of the CPU case, and four of them out in the front, actually on the top of the case, but they can be present anywhere. That allows me to connect eight devices to the computer in the simplest manner, which is plug-and-play. I only have to connect a USB compatible device through the port and it plays. I do not have to restart my computer.
In days of yore, even if you had to connect a mouse to your computer, you needed to restart the PC and wait till the almighty message 'Your new hardware is now installed and ready to use' came on. This was frustrating at times, because the computer would not detect the new device and that meant we had to do some physical jangling to set the device to work. Whatever it was, we needed to lift ourselves from our comfortable seats.
This is exactly what the USB has made redundant. Now, all you have to do is just push in the USB plug into any USB port of the computer and the device is ready to use. In almost all cases, detection of the device is not an issue at all. You won't even know how it happens and the wonderful square icon comes up into the bottom functions tray of your computer screen indicating that a new device has been plugged in.
So, what devices can be connected to the USB ports of the computer? Fortunately, almost every computer accessory is USB compatible nowadays. Keyboards and mice have seen their USB era (they are much, much ahead now, with wireless technology and even virtual keyboards that are just a holographic image without a physical body at all, but that's not our topic of discussion here).
External devices, like camcorders, digital cameras, printers, scanners, modems, speakers, scanners, webcams, cell phones, and iPods are all compatible with USB ports. It is not just the PC that has USB ports. You can find them on laptops, PDAs, and game consoles too. You can even connect a laptop to the PC through a USB. I am not sure if there's a USB cable designed to connect one computer with another, but there must be.
Cables and Connectors
In fact, the main part of any USB compatible device will be the cable and the connector attached to it, which is supposed to be plugged into any USB port to operate the device. The computer is designed to understand the device automatically when the USB cable is connected, without needing any rebooting or inserting installation cards.
Generally, the USB cable and connector are inbuilt onto the device. Such connectors are called A-type connectors. Sometimes, there is no direct connection, but there's a socket that accepts a USB connector. These connectors are different in structure from the A-type, and are, hence, called B-type connectors. By function, A-type connectors will head in the direction of the computer, while B-type connectors will head to the device.
Ports and Hubs
The USB port is the socket-like region on the PC, or whatever device you are using, where the USB connector is supposed to the plugged. The number of USB ports on computers are increasing with each passing day―finding even 4 USB ports on notebook computers is considered to be quite commonplace. Typically, one USB port will provide a data transfer rate of 12 Mbps.
Today, with most of the peripheral devices turning out to be USB compatible, it is quite easy for someone to run out of USB ports. For this reason, people use USB hubs. These hubs contain several inflow and outflow USB connecting areas on them. A hub can contain as many as 127 connections for peripheral devices, and the simplest design is the 4-port USB hub. You will also find hubs that need power supply, as well as those that can do without it.
What is USB 2.0?
The USB 2.0 is the advanced version of the USB 1.1 which was being used worldwide until now. This is a high speed USB connection, which can provide a data transfer rate of up to 480 Mbps, but you can step down to 1.5 Mbps and the common 12 Mbps if you want to. Another striking achievement of USB 2.0 is that it allows both backward and forward compatibility with the older version USB devices.
USB has changed the way devices interact with computers, and development is still ongoing. USB 3.0 is already here, with more improvements over the 2.0 standard. The day is not far where all peripherals will be USB compliant, and wireless, so we won't have to bother with even cables.