Data Acquisition

With the advent of Windows as a graphical interface we have gone from Windows 3.11 to95 and NT, to 98 and now Windows 2000. It has been the direction of the MicrosoftCorporation to move the PC operating system away from DOS. This has been done for manyvery good reasons. DOS had many problems, the worst of which was the memory allocationsystem. Microsoft used 95 and 98 as small steps to move the PC operating system further andfurther away from DOS. 2000 and NT do not use DOS at all. These operating systems haveone major problem when it comes to data acquisition. It is in the timing. The graphicalinterfaces from 95 and up do not consider the peripherals as high priority. Windows itselfconsiders the operating system as the most important thing in the computer. The 95 andhigher computers do true multitasking with every window opened as a virtual computerwithin the computer. Even applications that are not viewable by the user i.e. running in thebackground, are handled like virtual computers. This means that if the operating system,background program, or running application, need service, the operating system decides whois serviced. Just because a data acquisition program is running, it does not mean that it willhave high priority. Timing therefore cannot be guaranteed when using these operating systems.Due to this problem, data acquisition users and designers have often looked elsewhere foran operating system that will guarantee direct access to the data acquisition system. Somehave locked themselves into DOS while others have tried UNIX. The problem with theseoperating systems is that they have their own problems. DOS is old and not supported byanyone, including Microsoft. UNIX is limited by the software available and a good graphicalinterface. This may change with Linux. The best one can do is not use Windows productswhen timing is critical, especially when the computer is used to control a time criticalprocess, or alternatively, to strip everything off the computer except the data acquisitionprogram. However, even this will not guarantee correct timing.Some of the advantages of Microsoft Windows are:• Standard graphical user interface for all applications• Natural user interface that is easy to learn and use• Application programs that are independent of system devices• Multitasking support• Support for dynamic data exchange• Virtual memory managementMultitaskingMultitasking is the ability of the operating system to run multiple application programssimultaneously. With Microsoft Windows, you can execute two or more application programsat the same time. Each application has its own window allowing the user to switch betweenapplications.Graphical user interfaceThe graphical user interface allows the user to execute application programs, by simply selectinga graphic symbol or icon representing that application. Icons are small symbols thatare used to represent files, programs, or program tools.Graphical user interfaces are important for computer systems because they provide symbolicinterfaces, giving the user visual or graphic control over program execution. It alsoprovides a common interface with the user for all application programs, making it easier tolearn new application programs. At the same time, graphical user interfaces provide softwaredevelopers with visual tools for developing programs that take advantage of the userinterface.