With this new section, the serial communications are allowed from
 CA-Clipper. The functions are low level and realize an Interrupt Driven
 Service task of the serial ports from CA-Clipper.

    It's allowed to manage 4 serial ports, from COM1 to COM4 on AT systems
 and 2 ports, COM1 and COM2 on XT systems.

    The system is compatible with all kind of current UART's existing in
 the market for PC-XT-AT cause can access to the system via 8259A therefore
 the BIOS routines are taking charge of the UART'S compatibility.

    The system has available internal and external buffers circulars of the
 same kind than the BIOS has available for the keyboard. Thanks to them,
 we have available the incoming and outgoing datas in memory until the
 moment that we were interested to pick up or send them. The incoming buffer
 has been established in 16384 bytes and the outgoing buffer in 4096 bytes.