Supported Platforms: Windows and Mac OS
Type: T or nil
T if sym has a value bound to it. If no value is bound to sym, or if it has been bound to nil, boundp returns nil. If sym is an undefined symbol, it is automatically created and is bound to nil.
(setq a 2 b nil)
The atoms-family function provides an alternative method of determining the existence of a symbol without automatically creating the symbol.