ABSTRACT
This chapter discusses the structure of General Purpose Simulation System (GPSS) models and some of the basic features of GPSS. GPSS programs consist of a sequence of control and executable statements. The executable statements, called blocks, describe the logic of the flow of transactions through the simulation. The mere presence of executable statements within a GPSS program, however, does not cause any action to occur. To simulate the use of parallel servers, GPSS provides a storage entity that represents a predetermined number of identical servers. A transaction can capture a server as long as there is one available; furthermore, a transaction can capture several servers simultaneously if the needed number of servers is available. A common error among GPSS beginners is to associate queue membership with the location of the transaction in the QUEUE block. After entering a QUEUE block, a transaction becomes a member of the queue specified by the A operand of the QUEUE block.
