HP Data Entry and Forms Management System (VPLUS) Reference Manual (32209-90024)

588 AppendixE

Application Hints

Rules for the DL Area

VPLUS makes use of the DL area for buffers and internal tables. Therefore, if the DL area

is put to any other use during the execution of a VPLUS application, such use must not

conﬂict with that of VPLUS. To insure against conﬂict, observe the following rules:

1. The ﬁrst use of the DL area by an application, including any procedures, routines, or

intrinsics executed on behalf of the application, should be the call to VOPENFORMF that

opens the forms ﬁle and allocates the DL area needed by VPLUS.

2. The call to VCLOSEFORMF that frees up the DL area used by VPLUS must not occur until

the application has released all other DL space allocated subsequent to the VOPENFORMF

call.

These restrictions need not be followed if the application is wholly coded in any

combination of Pascal, HPFORTRAN 77, and HPBUSINESS BASIC and sets the comarea

item language to 5, which causes VPLUS to use the heap procedures provided by Pascal

instead of managing the DL area directly.

VPLUS applications coded in other languages need to take great care if they pass the

language

identiﬁer of 5 as a means of getting around the restrictions stated above.

Specifying an incorrect language identiﬁer can cause other aspects of the VPLUS

interface, such as addressing of byte parameters, to function unreliably. In such a case, the

application must use the INTRINSIC mechanism (CALL INTRINSIC in COBOL) for the

main and all interacting parts of the application. Check the Pascal and COBOL reference

manuals for more information.

In all cases, check for any other use of the DL area by intrinsics such as the DSG intrinsics.