Hardware Reference
In-Depth Information
reasonably intuitive and the user should not be presented with outcomes which
he or she did not expect. As an example, it should not be possible to quit from a
package without being presented with a clear warning of the consequences (e.g.
data loss). Similarly, on-screen controls and displays should, as far as possible,
mimic those which the user will already be familiar with. All this may sound
very obvious but programmers and software engineers often fail to identify
with the level of expertise of the operator, and he or she may be left to 'muddle
through' by trial and error.
Fortunately, there is a trend towards making software 'user-friendly' and
this has been greatly aided by the availability of graphics-oriented operating
systems such as Microsoft's Windows with programs that are designed to take
full advantage of the visual environment. Such packages can be highly intuitive
and provide an excellent user interface based on windows, icons, and pull-down
menus (WIMP).
The WIMP interface is also available to any application that is co-resident
with the operating system. Because of this, an application that needs to make
use of the WIMP environment can simply make calls to appropriate system rou-
tines obviating the need to create its own stand-alone routines for manipulating
windows and other graphical components.
Flexibility
Some software packages (particularly those which may have been written for a
particular application) tend to be somewhat rigid since they are generally based
on a pre-defined model. In many cases, such programs will not provide the
operator with an opportunity to configure the system or select from a range
of choices (e.g. via a menu screen). If a change does become necessary, the
software has to be modified at the source code level. Sometimes this task can
be tackled by a keen control engineer but, more often than not, it will require
the services of a programmer or software engineer.
More flexible software packages will allow the user to configure the software
for a particular hardware system (e.g. by specifying the system components and
expansion capability) or, alternatively, will use plug-and-play capability when
the operating system supports this. In all cases it is important to ensure that the
installation and configuration process is made transparent to the user.
As users become fully aware of the advantages of a PC-based instrumentation
and control system, a further consideration which will often become increas-
ingly important is that of interfacing with other software packages so that data
can be exported and imported in a fashion which is largely transparent to the
user. This is often advantageous where measurements must be made within one
program before the captured data (stored in a disk file) is imported into another
program for statistical and/or graphical analysis. This opens up a completely
new scenario in which data acquired by one program can be made to yield all
manner of new information when analysed by another package. The availability
of Dynamic Data Exchange (DDE) has made it possible for data to be exchanged
on a transparent basis between suitably equipped programs. For example, DDE
makes it possible to data sourced by a custom-written application to appear in
an Excel spreadsheet without the need to first export the data and then import
it into Excel.
