RS-232C, EIA RS-232, or simply RS-232, refers to the same standard defined by the Electronic Industries Association in 1969 for serial communication.
RS-232 is a standard for serial communication transmission of data. It formally defines the signals connecting between a DTE (Data terminal equipment) such as a computer, and a DCE (Data communication equipment), such as a modem.
A straight-through cable is used to connect a DTE (e.g. computer) to a DCE (e.g. modem), all signals in one side connected to the corresponding signals in the other side in a one-to-one basis. A crossover (null-modem) cable is used to connect two DTE directly, without a modem in between.
