Sir, I am using gcc 4.6.1. I have few questions regarding -lm switch. Please kindly guide me for the same. 1) Why I need to use -lm flag for math.h even if I had declared the #include <math.h> in the code? 2) If it's all about linking the library then why I don't have to do the same thing with stdio.h too? 3) Or we have to add the -l'library' switch for every library excluding stdio.h? 4) In case if the -l'library' switch is used for some specific libraries only then please direct me to the complete list of such libraries. Thanks. -- Avinash Sonawane PICT Pune India