IF within a subroutine
AND
a "+" (debatable superfluous) sign is prepended to a positive coordinate i.e X +0.100 instead of just X 0.100
the simulator will ignore (set as RED comment) the plus sign AND all instructions to the right of it on the same line.
You can see in the G code that the "+0.100" will be turned to red...like it is treated as a comment..so the move to the coordinate will not happen.
If you do the same "X +0.100" NOT within a subprogram only the superfluous "+" will be made red (ignored) but not everything to the right on that line ..so the code will still move to the coordinate as intended.
(The reason I sometimes like to use the superfluous "+" is so I can be sure I assigned it the correct sign and did not just neglect to assign the "-" )