Page "RS-232" Paragraph 24

In the book PC 97 Hardware Design Guide, Microsoft deprecated support for the RS-232 compatible serial port of the original IBM PC design.

Today, RS-232 has mostly been replaced in personal computers by USB for local communications.

Compared with RS-232, USB is faster, uses lower voltages, and has connectors that are simpler to connect and use.

However, USB is limited by standard to no more than 5 meters of cable, thus favoring RS-232 when longer distances are needed.

Both standards have software support in popular operating systems.

USB is designed to make it easy for device drivers to communicate with hardware.

However, there is no direct analog to the terminal programs used to let users communicate directly with serial ports.

USB is more complex than the RS-232 standard because it includes a protocol for transferring data to devices.

This requires more software to support the protocol used.

RS-232 only standardizes the voltage of signals and the functions of the physical interface pins.

Serial ports of personal computers are also sometimes used to directly control various hardware devices, such as relays or lamps, since the control lines of the interface can be easily manipulated by software.

This is not feasible with USB, which requires some form of receiver to decode the serial data.