Address declaration in Scilla

gistfile1.txt

contract Address()

field a: Option ByStr20 = None {ByStr20} (*declaring variable a with no value*)
field b: ByStr20 = 0x1234567890123456789012345678901234567890
(*declaring variable b with some fixed value*)

transition update_value()

   (*updating variable a*)
   c = 0xabcd567890123456789012345678901234567890; (*declaring variable c with fixed value in the transition*)
   tmp= Some {ByStr20} c;
   a:= tmp;
    
   (*updating variable b*)
   d= 0xffff567890123456789012345678901234567890;
   b:= d
   
end