Hi, I am not sure if my subject has a good title, but anyway.. I declared a variable to be an integer, and incremented after certain tasks. It turned out that the value of the integer exceeded 2^15-1 = 32767 and took on the value of -32768, then -32767,,, etc.. My program continued chugging along without a care in the world. Is there any way to force IDL to tell you that something like this is happening and maybe stop? If not, it would be a very useful addition. Thank you very much. -Rob