I am feeling a little controversial today so forgive the blunt title of this post I have never used global variables because I was under the misconception that they are somehow "bad". That is all I have heard from the time I started learning LabVIEW. Look at code in the upconvert and downconvert threads. Some of the ugliest code uses globals and some of the most beautiful code does not. This implies that bad programmers use global variables and therefore globals are bad programming practice. This is not true. Globals are just easy to use so beginners use them. "Uninitialized what? I can't find those on the pallette?" I think I always subconsciously questioned that globals are bad. They are not bad it is how they are used that can be bad. This is true of anything in life. The first and most obvious problem with global variables is race conditions. But it is not strictly the global that causes the race condition. It is the undefined dataflow. But the same is true of a functional global if used incorrectly. In the example below there is nothing to enforce dataflow. You need to enforce the dataflow with an error wire for example. Globals do not have an error wire but not to fear - the sequence man is here! You only need the sequence if the global is directly on your block diagram. Those two single frame sequence structures could be replaced with a NumericWrite.vi and a NumericRead.vi containing nothing but the global, a control or indicator respectively, and the error terminals. Set them to inline and you are good as gold. Or you could have one subvi containing nothing but a two frame case structure selected by an enum containing the items "Get" and "Set". It now looks like a duck and quacks like a duck. Don't worry about overhead from the case structure either. If the enum is a constant it will be folded out. Another problem with globals is that they are, well, global. This is no different from a functional global so it is not really an issue anyway. For both globals and functional globals this is easily addressed by placing them in a library and setting the access scope. Besides that libraries give you namespaces and "Namespaces are one honking great idea -- let's do more of those!" * The real reason to use a global instead of a functional global is that they are about twice as fast. Up until this morning I would have recommended to use a functional global over a global. But I changed my mind. Can anyone change it back? * The Zen Of Python

I go on vacation for a week and I come back to this? Dogs and cats living together... In this thread I swore off Globals once and for all. Flat out bench-marks on just the global may trick you into thinking they are faster but they simply do not allow working in-place. Ease of support is another big factor. Re: call overhead It is a standard to include "extra" terminals on an icon connector but I have benchmarked the "extra terminals" and the call over-head scales with the number of extra copies. Data copies and the most frustrating part ofa global is, you can not do a ctrl-e to fix it. Ben

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