Serial cables are used for transferring information between two devices directly. The serial communication protocol is used by serial cables for such transfer. Also, to connect the cables from the devices, connectors are used which relies on the specific serial port used. In serial communications, serial means that one hit after another is sent out onto a wire or fiber. This is very different from parallel communication where bits are sent in groups. In serial cables, the bits are interpreted by a network card. Each 1 or 0 is read separately and then combined with others to form data. In parallel communication, bits have to be read together to be able to represent their meaning. Following are the standards of serial cables:
Recommended Standard 232 (RS-232): Refers to a standard commonly used for serial data signals connecting data terminal equipment and data communication equipment. This standard is now replaced by Universal Serial Bus (USB) and FireWire.
USB: Refers to a standard that is used to transmit information between devices using serial communication. USB ports are built-in serial bus in most of the motherboards. You usually get four external USB ports; however, you can use up to 16 USB ports using add-on adapters. Nowadays, you can use USB to connect devices, such as printers, scanners, and keyboards. When connecting USB peripherals, you need to connect them either directly to one of the USB ports on your computer or to an add-on adapter that is connected to one of those USB ports.