In the instruction PR[i, j], what does i represent?

In the instruction PR[i, j], the value of i specifically indicates the position register to use. Position registers are used in FANUC programming to store coordinate data points or paths that the robot can reference during operation. These registers allow the robot to remember specific locations or movements that have been defined earlier in the program.

When you specify PR[i], you are essentially directing the system to access and utilize the defined coordinates or movements stored in the designated position register 'i'. This is a critical aspect of programming with FANUC systems, as it allows for flexible and efficient programming by enabling the reuse of previously defined positions without having to re-enter their coordinates each time.

Thus, understanding the role of the position register is key to effectively implementing motion commands and coordinating the robot's actions during operation.