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

Appendix L 671
A Programmer’s Guide to VPLUS
Optimizing VPLUS Utilization
needs to access at one time. Assuming there is enough information to fill the screen, does
one want to show it all at once. Too much data may overwhelm the user, making data entry
more difficult due to a crowded and confusing screen. Presenting data in small doses may
frustrate the user as he moves through multiple forms to see all the data, making data
entry that much longer.
Here, the old “space/time” tradeoff comes into play: by saving the space needed for the
display of data (in the multiple-form scheme), more time is needed for showing all screens,
while by displaying all the data at once, more space is needed (but all necessary
information is shown in one pass). One advantage to the multiple-form method is that a
user could stop viewing the screens of data once the needed data is displayed (assuming
such an escape mechanism is designed into the program).
If you decide to use the one-screen approach, there are many things you can do to avoid
problems before they occur. One is to keep the amount of data (in number of bytes) equal
between forms in the forms file. This will enable VPLUS to get the greatest amount of
utilization from the DBUF and IBUF, since there would then be only a few instances where
just portions of each were needed for I/O operations. Another is to keep the number of
fields as equal as possible between forms. This will allow VPLUS to get the greatest
amount of utilization from the FST and other internal tables connected with field
manipulation on each form.
Reducing the Size of Large Fields
If some forms in the forms file are composed of many small fields, while there is also a form
with one or two VERY large fields (for example, a program where general information is
needed about a person, but specific comments may be made), you might consider changing
the form with those large fields into a form with smaller fields.
A good example of this is one where the entire screen is an unprotected field for text entry.
That form would only need one entry from the FST (since there’s only one field), but would
require 80*24=1920 characters for the DBUF and IBUF. Changing this form to one which
repeats, appends to itself, and is made of only one 80-character long field will allow the
same functionality of the former form (with the exception of having to press
ENTER at the
end of each line), and actually be more flexible. This flexibility comes from the fact that
now the user can input as many lines of text as are needed, whereas before they were
restricted to 24 lines.
Similar things can be done to the form which has the largest number of fields. If the fields
are some sort of tabular data, making another repeat/append type form set can help. In
this set, the first form could contain header information, while the second is a
self-repeating and self-appending form containing the fields for each detail line.
Using Forms Families
Another trick to speed up the display of forms is the effective use of forms families. Forms
families are sets of forms which share a common screen definition, but different field
characteristics. Any time a forms family member is to be displayed, VPLUS checks to see if
the last form displayed was another member of that same family. If it was then instead of
transmitting the entire form definition, VPLUS sends only those escape sequences needed
to alter those fields that differ between the forms (e.g., from unprotected to display- only,
from half-intensity inverse to underlined blinking, etc.). If all of the information to be