ORTHOMODE system variable
Function Description:
The ORTHOMODE system variable is used to constrain cursor movement in perpendicular direction.
Type : Integer 
Saved in : Drawing 
Initial value : 0 
Range : 0,1 
When the ORTHOMODE is on, the cursor could move horizontally and perpendicularly relative to UCS and current grid rotation angle.
System Variable Value:
0 : turn ortho mode off
1 : turn ortho mode on