Programming Research Group  -  University of Amsterdam  -  TR P9811


		Program Algebra for Component Code


			  J.A. Bergstra
			    M.E. Loots


The  jump  instruction  is  considered  essential  for an  adequate
understanding of imperative  sequential  programming.  Using atomic
actions  and tests as a basis we outline an  algebra  of  programs,
denoted PGA, which  captures  the crux of  sequential  programming.
PGA provides an ontology for programs rather than a semantics.  Out
of a multitude of conceivable semantic views on PGA we single out a
semantical  abstraction  operator  which  assigns to each program a
behavior.  The  meaning of the  constants  of PGA is  explained  in
terms  of  behavioral  abstraction   semantics.  Based  on  program
algebra we define the general  concept of a sequential  programming
language.