Serial port, this one, (http://en.wikipedia.org/wiki/Image:RS-232.jpeg) it is usually coloured green on modern computers.
RS-232
A good alternative for a RS 232 would be modern USB ports. The RS 232 is a serial binary single ended data port. This port is common on computers; however, recently this port has been replaced by USB ports.
The "com" ports are computer, serical communications ports (normally RS-232).
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RS-232 is used over serial ports, which are typically found on computers and various electronic devices for communication. It transmits data one bit at a time, using a standard defined by the EIA (Electronic Industries Alliance). Commonly, RS-232 ports are DB9 or DB25 connectors, though modern devices may use USB-to-serial adapters to facilitate RS-232 communication.
RS232 is a communications protocol for electronic devices to exchange information
RS-232 serial ports, Parallel ports, and PS2 mouse and keyboard ports. These days, all of these functions can be handled by Universal Serial Bus (USB ) connections.
The 232 doesn't stand or come from anywhere. It's just a reference number. RS-232 = Recommended Standard 232
Recommended Standard 232
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RS-232 serial ports are far slower than USB ports. With very few exceptions, devices that use USB ports would be impractical to use on a serial port.
Legacy ports typically refer to older communication ports that have largely been replaced or are less common in modern devices. Examples of legacy ports include the RS-232 serial port, the parallel port, and the PS/2 connector for keyboards and mice. These ports were widely used in earlier computing and peripheral connections but have largely been superseded by USB and other newer interfaces. Their continued use is often limited to specific applications or older hardware systems.