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

670 AppendixL
A Programmer’s Guide to VPLUS
Optimizing VPLUS Utilization
Optimizing VPLUS Utilization
VPLUS, Hewlett-Packard’s standard terminal management software, finds wide use in
applications ranging from manufacturing control to financial transaction processing.
Offered as part of the HP3000 Fundamental Operating Software (FOS), VPLUS provides
programmers and designers access to the features of HP block-mode terminals, effectively
insulating programs from the details of data communication and terminal control.
The Response Centers receive many questions regarding VPLUS optimization and
program performance. This Note will address several topics related to these issues. There
are three major areas where even small amounts of effort from the programmer can make
significant differences in VPLUS performance:
• Effective forms design
• Stack use by VPLUS applications
• Programs’ utilization of forms and forms files
A proper balancing of effort in all three areas can help you make significant strides
towards efficient use of VPLUS.
A working knowledge of FORMSPEC and “general principles” of forms file management is
assumed, as is knowledge of the major VPLUS routines (e.g., VGETNEXTFORM,
VSHOWFORM, VOPENTERM).
Definition of Terms
In this Note we shall discuss what changes need to be made to the largest form in the
forms file targeted as being troublesome. There are many valid definitions of “largest
form”. One is “that form in which the largest amount of data is transferred between the
program and terminal”. Another is “that form which contains the largest number of fields”.
A third is “the form which, when displayed on the terminal, uses up the most space on the
“screen”. When the term “largest” is used, it will be further defined for its context.
There are also three acronyms used throughout this paper. FST stands for Field Status
Table, and is used by VPLUS to hold information about each field on the current form.
DBUF and IBUF refer to the Data BUFfer and Input BUFfer used internally by VPLUS. Any
program (through calls to VPUTBUFFER and VGETBUFFER) can manipulate the DBUF, while
the IBUF is a reordering of the DBUF and is used internally by the VPLUS intrinsics for
data transfer to and from the terminal.
Effective Forms Design
One of the easiest and least painful ways to help the performance of programs using
VPLUS is to use foresight in designing the forms to be used by those programs. A few
simple tricks applied in advance can save a lot of debugging and redesign later in the
process.
One Screen Approach
One of the first things to keep in mind when designing forms is how much data the user