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From: "Olivier@ucbvax.UUCP
Newsgroups: mod.computers.vax
Subject: RE: How does (vms) help use ?
Message-ID: <8606181053.AA10776@ucbvax.Berkeley.EDU>
Date: Wed, 18-Jun-86 04:02:37 EDT
Article-I.D.: ucbvax.8606181053.AA10776
Posted: Wed Jun 18 04:02:37 1986
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> The vms help program uses the ? (question-mark) key in a special way.
> Immediately after the ? key is pressed, help proceeds to display the
> current help page, which usually has an index of help subtopics. Can
> someone show me how a program could do that, set up certain keys to
> cause interrupts (or whatever you call them in vms land)? Thanks.
 
> On the side, I've always wondered why help couldn't read what was on
> the input line before the ? instead of throwing it away... Or why couldn't
> DCL do a similar thing ala TOPS-20... Just a thought.

> George Boyce, Academic Computing, Cornell Computer Services
> george@vax1.ccs.cornell.edu (128.84.252.10)
> george@crnlcs.bitnet

Here is a Fortran subroutine (READ) using a QIO system service ala VMS-HELP
The second subroutine (ANALYZ) treats ascii character 63 (?); this shows how
HELP can ignore the string preceding "?".

Olivier Marchand - Etudes et Productions Schlumberger (France)
"OMARCHAND%EPSVXE@SLB-DOLL.CSNET"

	SUBROUTINE READ(LU,RDLTH,IOSB)
	IMPLICIT INTEGER (A-Z)
	INTEGER*2	CANAL
	INTEGER*2	FINI1(2)
	INTEGER	  	FINI(2)
	INTEGER		IOSB(2)
	BYTE		MASK(8)
	INTEGER*2	RDLTH
	INTEGER*2	PRLTH	/7/
	CHARACTER*512	LU
	CHARACTER*7	PROMPT	/'Topic? '/
	CHARACTER*11	TERMINAL	/'SYS$COMMAND'/
	EQUIVALENCE	(FINI,FINI1)
	INCLUDE		'($IODEF)'
c	-------------------------------------
	STATUS = SYS$ASSIGN(TERMINAL,CANAL,,)
c	-------------------------------------
	IF (.NOT. STATUS) STOP 'Error assigning a channel to SYS$COMMAND'

c we need 64 bits (=8 bytes) to be able to set bit number 63.
	FINI1(1) =  8
	FINI (2) = %LOC(MASK)
c			Zero mask
	DO I = 1, 8
	MASK(I) = 0
	ENDDO
c			set  bit  13 (ascii character 13 "<CR>" is a terminator)
	MASK(2) = 2**5
c			set  bit  63 (ascii character 63  "?"   is a terminator)
	MASK(8) = 2**7
c	-------------------------------------
	STATUS = SYS$QIOW(%VAL(5),
     &			%VAL(CANAL),
     &			%VAL(IO$_READPROMPT),
     &			IOSB,,,
     &			%REF(LU),
     &			%VAL(RDLTH),,
     &			%REF(FINI),
     &			%REF(PROMPT),
     &			%VAL(PRLTH))
c	-------------------------------------
	IF (.NOT. STATUS) STOP 'Error during read'
	RETURN
	END

	SUBROUTINE ANALYZ(STRING,LULTH,IOSB)
	CHARACTER*512	STRING
	INTEGER*2	IOSB(4)
	INTEGER*2	LULTH
	INTEGER*2	STATUS
	INTEGER*2	LENGTH
	INTEGER*2	TERMIN
	INTEGER*2	TRSIZE

	STATUS = IOSB(1)
	LENGTH = IOSB(2)
	TERMIN = IOSB(3)
	TRSIZE = IOSB(4)

	IF ((LENGTH.EQ.LULTH).AND.(TERMIN.EQ.0)) STOP 'String too long'
	IF (TERMIN.EQ.63) CALL DO
	RETURN
	END