The Basic Development Environment consists of a number of package groups (libraries) that build upon the libraries below them to provide higher and higher levels of functionality for application developers.
The lowest layer of BDE is the Basic Standard Library, which is an implementation of the C++ standard library with enhancements that can be used to directly manage memory usage, provide defensive programming support, and more.
The next layer of BDE, which uses functionality from BSL, is called the Basic Development Library. It provides memory allocation mechanisms to support a number of different usage patterns and test driver support functions. This library is where the BDE team is focusing much of its development efforts, and the near future will see many more packages and components released.