1	SUB VISOPN
2	! will open visual 500 on lun=.VIS5LUN% with ALUN$ & IOATT directive.
3	! assumes visual 500 is device VI0:
4	! ERR$ is a 4-byte IO status block.
5	! inspect ERR$ in COMMON (VIS500) to find if open of visual 500 worked.
6	COMMON (VIS500) VIS5LUN%, QIOW$=2%, ERR$=4%, VIS5EFN%, ERRADR%, CHARMASK$=32%, CMADR%
7	.DEFINE .VIS5LUN% = 29%	! visual 500 lives on this lun
8	.DEFINE .VIS5EFN% = 32%	! an event flag number for waiting on visual 500
9	VIS5LUN% = .VIS5LUN% \ VIS5EFN% = .VIS5EFN%
10	.DEFINE .ALUN% = 1031%	! ALUN DIR$ code
11	.DEFINE .IOATT%=768%	! IO.ATT QIOW$ code
12	.DEFINE .VISD$="VI"
13	.DEFINE .MCU%=0%
14	LSET CHARMASK$ = STRING$(32%,255%)
15	CALL ADR BY REF (CHARMASK$,CMADR%) ! know address of character mask for input
100	CALL DIR BY REF (.ALUN%,VIS5LUN%,.VISD$,.MCU%)	! attach visual 500
110	CALL ADR BY REF (ERR$,ERRADR%)	! know IO status block address
120	LSET QIOW$ = CHR$(3%)+CHR$(12%)	! know QIOW$ constant
130	CALL DIR BY REF (QIOW$,.IOATT%,VIS5LUN%,VIS5EFN%,ERRADR%,0%,0%,0%,0%,0%,0%,0%)	! open visual 500
140	! ERR$ contains on return:
150	! byte#1:	directive status	(should be 1% for sucess)
160	!      2:	further details code
170	!      3:	?
180	!      4:	?
190	SUBEND