Disclosed is an application program which can directly access a transmit buffer of a serial port. Data written into the transmit buffer by the application program is transferred into a receive buffer of the serial port via a switching element. The computer BIOS is enabled to directly access the receive buffer and therefore read the data written by the application program. The state of the switching element may be controlled by the application program to selectively allow data transfer from the transmit buffer to the receive buffer. A jumper plug may be used to create a short circuit between the transmit buffer and the receive buffer instead of closing the switching element.