diff --git a/matlab/SetBoundaryCond.m b/matlab/SetBoundaryCond.m
index 6d1ba6d..ed5ba8c 100644
--- a/matlab/SetBoundaryCond.m
+++ b/matlab/SetBoundaryCond.m
@@ -1,4 +1,8 @@
 function FDTD = SetBoundaryCond(FDTD,BC)
+% FDTD = SetBoundaryCond(FDTD,BC)
+%
+% BC = [xmin xmax ymin ymax zmin zmax];
+% ?min/?max: 0=PEC 1=PMC
 
 FDTD.BoundaryCond.ATTRIBUTE.xmin=BC(1);
 FDTD.BoundaryCond.ATTRIBUTE.xmax=BC(2);