Int 20

INT 20 - Minix - SEND/RECEIVE MESSAGE
AX = process ID of other process
BX -> message
CX = operation (1 send, 2 receive, 3 send&receive)

Program: Minix is a Version 7 Unix-compatible operating system by Andrew Tanenbaum

Note: The message contains the system call number (numbered as in V7 Unix(tm)) and the call parameters