module case_compare;

reg sel;

initial begin
  #1 $display ("\n     Driving 0");
  sel = 0;
  #1 $display ("\n     Driving 1");
  sel = 1;
  #1 $display ("\n     Driving x");
  sel = 1'bx;
  #1 $display ("\n     Driving z");
  sel = 1'bz;
  #1 $finish;
end

always @ (sel)
case (sel)
  1'b0 : $display("Normal : Logic 0 on sel");
  1'b1 : $display("Normal : Logic 1 on sel");
  1'bx : $display("Normal : Logic x on sel");
  1'bz : $display("Normal : Logic z on sel");
endcase

always @ (sel)
casex (sel)
  1'b0 : $display("CASEX  : Logic 0 on sel");
  1'b1 : $display("CASEX  : Logic 1 on sel");
  1'bx : $display("CASEX  : Logic x on sel");
  1'bz : $display("CASEX  : Logic z on sel");
endcase

always @ (sel)
casez (sel)
  1'b0 : $display("CASEZ  : Logic 0 on sel");
  1'b1 : $display("CASEZ  : Logic 1 on sel");
  1'bx : $display("CASEZ  : Logic x on sel");
  1'bz : $display("CASEZ  : Logic z on sel");
endcase

endmodule