What is a serial port and how does it work?

The serial port is an Asynchronous port which transmits one bit of data at a time, usually connecting to the UART Chip. Serial Ports are commonly found on the majority of PC Compatible computers. Usually referred to as a DB9 or DB25 connection, both of which adhere to the RS-232c interface standard and defined in ISO 2110 and ISO 4902. D represents the shape of the connector if placed vertically as shown in the below illustrations. The number 9 / 25 indicating the number of pins found on the connector. DB9 Serial connections are now commonly found on modern PCs where DB25 is commonly found on older computers.

A serial port is used to connect external modems or an older computer mouse to the computer. It comes in two versions a 9-pin version (on the left) or a 25-pin model. The 9-pin is found on most newer computers. Data travels over a serial port at 115 kilobits per second.