is ready to leave the stage s 1 let it be wafer w in chamber c y position the robot at c y wait if necessary and move w from c y to its target chamber c x update a data structure defining the state of the cluster tool and go to step 1 5 position the robot at a chamber whose wafer is to leave the stage n first after the wafer is moved from stage n to a loadlock update the data structure and go to step 1 the variable s 0 1 n 1 represents the stage number in step 4 if s 1 there is always a wafer ready to leave stage 0 stage 0 is the loadlock in step 3 if s n 1 there is always an empty space to move a wafer into since stage n 1 is the loadlock again the phrase 34 scan the stage s 34 in steps 3 and 4 above means to scan a data structure describing stage s in procedural programming such a data structure may be a linked list or an array of records where each record describes a chamber this data structure is further described with reference to fig4 below in object oriented programming a chamber may be an object from a given class and.