module stimulus;
// Set up variables
reg A;
wire out;   
reg Clk;                // Always declared so can simulate based on clock
integer handle3, desc3; //You need to define these variables as integers
        
// Instantiate the D-register
dreg D1(A, Clk, out);

// Setup the clock to toggle every 1 time units
   initial
     begin
        Clk = 1'b1;
        forever #1 Clk = ~Clk;
     end   
   initial
     begin
        handle3 = $fopen("test.out");
        $shm_open("shm.db",1); // Opens a waveform database
        $shm_probe("AS");    // Saves all signals to database
        #7 $shm_close();   // Closes the waveform database
        #1 $finish;
     end 

   always
     begin
        desc3 = handle3;
        #1 $fdisplay(desc3, $time," A= %b, out=%b, Clk=%b", A, out, Clk);
    end
// Stimulate inputs  
initial 
begin
        #1 A = 1'b0;
        #2 A = 1'b1;
end
endmodule