INT 0C - IRQ4 - SERIAL COMMUNICATIONS (COM1) Desc: automatically asserted by the UART when COM1 needs attention, if the UART has been programmed to generate interrupts BUG: this vector is modified but not restored by Direct Access v4.0, and may be left dangling by other programs written with the same version of compiled BASIC Notes: on many PC's, COM3 shares this interrupt may be masked by setting bit 4 on I/O port 21h DOS 3.3+ revectors IRQ4 to a stack-switching routine unless STACKS=0 has been set in CONFIG.SYS. MS/PC-DOS use the IBM Interrupt Sharing Protocol (see #02568) when hooking this IRQ SeeAlso: INT 0B"COM2",INT 54"DESQview",INT 5C"DoubleDOS",INT 7C"GO32"