I have a peculiar problem with winavr/gcc. I created one project and am adding 'C' code and compiling it with no problems what so ever. Recently I created a new project (using PN) and when I compiled the code, I got an error such as timers and other control registers not known (first use) also the sei () and cli () functions not found. However when I included the io.h file the errors vanished. How is it that in one projec I do not get any errors though I have not included the io.h file and in another the compiler reports errors?