And unlike static, classes declared in an anonymous namespace are local to the file as well.

The auto keyword, added in C 11, allows you to define a variable without knowing its type.

In the Arduino IDE, though, if you add a tab and give the new tab a name that doesn’t end in ‘.cpp’ or ‘.h’ then the file is given an extension of ‘’ When you click the ‘Verify’ button, all the ‘.ino’ files are concatenated into a single ‘.cpp’ file.

C 11 introduced a series of fixed width integer types aliases that will give you the number of bits (in multiples of 8) you want. If you use int16_t for a variable you know it’s 16 bits, regardless of which Arduino is being targeted.

This usually isn’t a problem for small Arduino programs, but it’s good to be aware of it.

Okay, so now we know about internal and external linkages and how files are concatenated before being compiled. Well, we now know how to define variables so that they won’t leak into areas they’re not supposed to be.

C gives you tools to allow you to do this, such as namespaces and classes.

The lowly enum, however, leaks its entries into the surrounding scope: The variable ‘white’ can’t be defined because ‘white’ is part of an enum, and that enum leaks it’s entries into the surrounding scope.