.TITLE IO
        $IODEF
TTNAME: .LONG 20$-10$
        .LONG 10$
10$:     .ASCII /TT/
20$:
TTCHAN: .BLKW   1

        .ENTRY INIT,0
        $ASSIGN_S DEVNAM=TTNAME,CHAN=TTCHAN
        RET

        .ENTRY WRITEBUF,0
        MOVL @B^8(AP),R1
        $QIOW_S CHAN=TTCHAN,-
                FUNC=#IO$_WRITEVBLK!IO$M_NOFORMAT,-
                P1=@B^4(AP),-
                P2=R1
        RET

        .ENTRY READCH,0
        $QIOW_S   CHAN=TTCHAN,-
                  FUNC=#IO$_READVBLK!IO$M_NOECHO!IO$M_NOFILTR,-
                  P1=@B^4(AP),-
                  P2=#1
        RET
        .END