Outer loop index. When loops are nested, this pushes the value of the outermost loop onto the stack.

# Show the trace log, clear it, then show the result of multiplying 3 loop 
# indexes 
ShowTraceLog 
ClearTraceLog 
2 1 do 
	4 3 do 
		6 5 do 
			I J K mult mult trace 
			loop 
		loop 
	loop