Universal Serial Bus (USB)

Hello students, welcome to Kwickprep. Your phone charger, keyboard, mouse and pen drive all use the same kind of plug. Why did the whole world agree on it? Today we will learn what USB is, how it works, and its benefits and drawbacks for your exam.

USB stands for Universal Serial Bus. Universal means it is one standard that works with many kinds of devices. Serial means data is sent one bit at a time, down a single wire. Bus means a shared path that carries data between devices. USB is an industry standard, so any maker can build devices that follow it.

To understand the word serial, compare it with parallel transmission. In serial transmission, bits travel one after another on one wire. In parallel transmission, several bits travel at the same time on several wires. Over long cables, parallel bits can arrive out of step, which is called skew, so errors increase. Serial has no skew, so it is reliable over longer distances, and that is why USB uses it.

Let us see what happens when you plug a pen drive into a computer. First, the device is connected to the USB port. The computer automatically detects that a device is attached. The device tells the computer what kind of device it is. The operating system loads the correct device driver, which is software that lets the computer talk to the device. If no driver is found, the computer asks you to install one. Then data can be sent and received.

Exams often ask for the benefits of USB, so learn these carefully. Devices are detected automatically, and the driver is loaded for you. The connector can only fit one way, so you cannot plug it in wrongly, and the USB Type C plug is reversible. It is an industry standard, so it works on almost every computer, and newer versions are backward compatible with older ones. The cable can also supply power, so a mouse needs no battery and a phone can charge.

USB is not perfect, and exams ask for drawbacks too. The standard cable length is limited to about five metres, so it is not used for long distances. Older USB versions transfer data more slowly than some other connections. Very old devices may not work with the newest ports without an adapter. And the power supplied by a normal port is limited, so large devices need their own power.

USB has improved over the years, and speed is measured in bits per second. USB two point zero sends up to four hundred eighty megabits per second. USB three point two Gen one sends up to five gigabits per second. USB four sends up to forty gigabits per second. You do not need to memorise these numbers, but notice that each version is much faster.

The version is the speed, but the type is the shape of the plug. Type A is the older flat rectangle that fits only one way up. Type C is small and oval, and it fits either way up. Type C is now used on most new phones and laptops, and India has adopted it as a common charging port standard.

Pause the video and try this exam style question. A student says USB sends eight bits at the same time on eight wires. Is the student right? No, that describes parallel transmission. USB is serial, so it sends one bit at a time on a single wire for data in each direction.

USB connects many everyday devices to a computer. Input devices include keyboards, mice and scanners. Output devices include printers and speakers. Storage devices include pen drives and external hard disks. And phones use USB both to charge and to copy photos to a laptop.

Let us revise USB. USB stands for Universal Serial Bus. It is serial, so bits travel one at a time on a single wire. Devices are detected automatically and the right driver is loaded. The main benefits are that it is a standard, fits only the right way, is backward compatible and supplies power. The main drawbacks are the short cable length and slower old versions.