You will be told which line in your program caused the error, and be offered a chance to r epeat everything. There are 3 parts to each Monitor Command, and their order is important. If only a Speed Change or Execution Direction is supplied, the execution will not advance or retreat. B means retreat execution to the program's Beginning at the present speed. D means Display the Defined instructions that are currently executing.
E means advance execution to the program's End at the present speed.
I means trace Inside the supplied Instruction name. L means Look at an arbitrary portion of the world. O means change the execution Options. P means Print the definition of a defined instruction. Q means Quit the program at the fast speed.