Trying to Include C libraries to my Arduino Sketch

My C libraries like stdio.h and avr libraries are installed, but when I try to include it, it says file not found. Can you please help me?

Much Appreciated!

What IDE version?

Do you have the right board selected? What board are you using? Is it a custom board?

Thanks for your response.

IDE v 1.6.7. I'm just compiling right now. I'm not trying to upload it, but I get an error on compile.

Arduino IDE uses C++ so using "pure c" is possible right out of the box...

Oh yes that's true. I'm just trying to include the avr/io.h file, but it's not working.

DrAzzy: What board are you using?

Please answer DrAzzy's question. The board you have selected does matter even if you're only trying to compile. Which board do you have selected in the Tools > Board menu?