Expects: AH    01H
AL    byte to send
DX    COMM port number (0 to 3)
Returns: AH    bit 7=0 if no error;
else, bits 0-6 have Line Status see BIOS COM status codes
Info: Transmits the character in AL over the specified COM line.

Notes: The return status code cannot indicate a time out error, since
bit 7 is used to flag any error.  Thus, after any error, you
should use INT 14H 03H to get the full story on what went wrong.

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INT 14H 01H: Send a Character