Source Code
UpperCamelCase
Class and struct names.
lowerCamelCase
Member variable and member function names and global function names.
CAPITALS_AND_UNDERSCORE
Constants and a small number of inline functions (C++) or macros (C) that are provided in language bindings.
__CONSTANT__
Compile-time compiler constants (i.e. those that control source-code inclusion, such as __GLN__ or __64BIT__).
____FOUR_UNDERSCORE_PREFIX
Macros internal to a source file (macros of wider scope are avoided, except for the exception throwing macros which add trace information, so only file-specific macros are used, and they are named thus to avoid conflicts).

Documentation

Default Arguments
Default arguments to functions are indicated using the equals sign, in the form argtype argname = argdefault.