Semicoroutine

Each incarnations needs some block structure information (static and dynamic link, display or such like), a return label, n+1 label variables for the activation points of the cooperation (in the "semicoroutine" case) and of the n coprocedures and the space needed for parameters and locals.

Source: wiktionary

C# 2.0 added semi-coroutine functionality through the iterator pattern and yield keyword.

Source: wiktionary