Parallel ports were initially developed in the 1970s to link office computers to printers. They were made commonplace in the business when they were added to the IBM PC in the early 1980s. Parallel connectors eventually supported bidirectional transfers, but when USB ports made their debut in 1996, they were initially designed as an input and output medium. For attaching external hard drives, input devices, printers, and a variety of other accessories, business computers today employ USB connections.
After the Institute of Electrical and Electronics Engineers published the IEEE-1284 standard, the parallel port was upgraded into a bi-directional port that could theoretically support data transfer rates of up to 4 megabits per second and support status updates from external drives, scanners, and drives in addition to printers. Speeds of up to 12mbps were supported by the USB 1.0 original standard. USB 3.0, introduced in 2008, offers transfers up to 5gbps, which is more than 10 times faster than USB 2.0 and more than 1200 times faster than parallel ports. USB 2.0 supports 480mbps.
2) Power Capacity
Parallel ports transmit and receive data signals while also including a few extra pins for grounding, error checking, and control. The only source of power on a parallel connection are the signals, which are typically 12 mA or less in strength. In contrast, USB is made to carry electricity to support the devices that are plugged into it. The current carried by a conventional USB 1.0 or 2.0 plug is 500mA at 5V, however USB 3.0 boosts the current to 900mA. You can charge gadgets more quickly with the help of special charging ports since they can squeeze even more electricity into a USB connector.
3) Physical Size
There are large parallel connectors. Parallel ports on a PC make use of a 25-pin connector with two rows and, frequently, substantial thumb screws to support it. An even bigger Centronics connector is used by printers. However, USB plugs are comparatively tiny. They are less than an inch wide and only have four conductors. Even smaller USB ports include mini- and micro-USB.
The parallel port served as the industry standard for connecting printers in the 1980s and 1990s. But since the late 1990s, when USB has become more and more ubiquitous, parallel port technology has lost some of its lustre. Nowadays, only a small percentage of computers or other devices still use parallel ports. On the other hand, USB ports are widely available.