.iif ndf $ccbdef, .library "sys$Library:lib.mlb"
	.iif ndf ccb$l_ucb, $ccbdef
	.link "sys$system:sys.stb"/selective_search

        .entry  channel_to_ucb,^m<r2,r3,r4,r5>
        movzwl  @4(ap),r0                       ; Get channel in R0
        jsb     g^ioc$verifychan                ; Get CCB in R1
        blbc    r0,10$                          ; Quit on error
        movl    ccb$l_ucb(r1),r0                ; Get UCB address in R0
10$:
        ret
	.end