文档介绍：Concepts and Terminology
Conventional programs describe actions that
change the values of variables in discrete steps. Execu-
Language Design for . Graham tion of these actions by any processor takes a finite
Reliable Software Editor amount of time. This time is not a characteristic prop-
erty of the program, but rather of the employed proces-
Toward a Discipline sor. In the interest of generality, programs are usually
designed such that puted results are independ-
of Real-Time ent of the execution speed of their processor(s). The
obvious way to obtain time independence is to restrict
Programming programs to describing purely sequential chains of ac-
tions. Each action is initiated when its unique predeces-
Niklaus Wirth sor has pleted. Such a program is called a
Federal Institute of Technology (ETH), sequential program.
Zfirich, Switzerland and Apart from mercial necessity of cost ac-
Xerox Palo Alto Research Center counting, the reasons for introducing the notion of time
into the programmers' considerations are purely tech-
nical. The principal reason is putation can be
speeded up by the use of several concurrently operating
processors. Often processors are needed with special
Programming is divided into three major categories capabilities not shared by others (such as input/output
with plexity of reasoning in progr