Registers
  Entry in: Encyclopedia of Algorithms, Ming-Yang Kao, Ed., Springer, To appear.   Synonyms: Wait-free registers, wait-free shared variables, asynchronous communication hardware. Problem Definition: Consider a system of asynchronous processes that communicate among themselves by only executing read and write operations on a set of shared variables (also known as shared registers). The system has no global clock or other synchronization primitives. 
Paul M.B. Vitanyi (CWI and University of Amsterdam)