diff --git a/chip_design_working_variable.sv b/chip_design_working_variable.sv
index 5a18db5..63b5938 100644
--- a/chip_design_working_variable.sv
+++ b/chip_design_working_variable.sv
@@ -236,7 +236,7 @@ module add_sub_wrap_nbit #(
 ) (
     input wire [N-1:0] a_in,
     input wire [N-1:0] b_in,
-    input wire         add_sub_sel,
+    input wire         add_sub_sel, // 0 = add, 1 = sub
 
     output logic [N-1:0] result
 );