Error HDL : Sel has no source pin

[osma78]

,here is my HDL code for a Mux ;

CHIP Mux {
    IN a, b, sel;
    OUT out;

    PARTS:
       
        Not (in = Sel , out = notSel);
         And(a = a , b = notSel , out = v1);
         And (a = Sel , b = b  , out = v2);
         Or (a = v1 , b = v2 , out = out);
    // Put your code here:
}
 when i try to open the file in the harware simulatur , i get the error : Sel has no source pin ,.
 I have a Sel pin defined in the Input part in my code , i don't understand the origine of this error .
 I need a help  

[cadet1620]

Pin names are case sensitive. You have

Not (in = Sel , out = notSel);

The input pin is named "sel".

--Mark