Choices is written as an object-oriented operating system in an object-oriented programming language C++. As an object-oriented operating system, its architecture is organized into frameworks of objects that are hierarchically classified by function and performance. The operating system is customized by replacing subframeworks and objects. The application interface is a collection of kernel objects exported through the application/kernel protection layer. Kernel and application objects are examined through application browsers. Choices runs on bare hardware on distributed and parallel computers. Virtual Choices (VChoices) also runs under UNIX System V.