module hello();

   initial begin
      //display your name and class accout.
      // Write your code here.
      // for example
      // if your name is "Clark Kent" and class account is ee375501
      // the exact answer will be: 
      //
       $display("ee375501  Clark Kent\n"); //simply change the account number and name.
      
   end

endmodule


////////////////////////////////////////////////////////////////////////////////
/// Problem 2
///

module neq_slice_es(eo,a,b,ei);
   input a, b, ei;
   output eo;

   wire   aneb, aeqb;
   
   // your solution goes here  
     xor x1(aneb,a,b);
     and a1(eo,aneb,ei);

endmodule


////////////////////////////////////////////////////////////////////////////////
/// Problem 3
///

module neq_slice(eo,a,b,ei);
   input a, b, ei;
   output eo;

   // your solution goes here
    assign eo = ( a != b) && ei;
        
    
    
endmodule


////////////////////////////////////////////////////////////////////////////////
/// Problem 4
///

module nequal(eq,a,b);
   input [3:0] a, b;
   output      eq;

   wire        e1, e2, e3;

   // your solution goes here

   neq_slice_es es3(e3,a[3],b[3],1'b1);
   neq_slice_es es2(e2,a[2],b[2],e3);
   neq_slice_es es1(e1,a[1],b[1],e2);
   neq_slice_es es0(eq,a[0],b[0],e1);



endmodule


////////////////////////////////////////////////////////////////////////////////
/// Test Bench
///

// Do not modify test bench


module test();

   reg abit, bbit, ei;
   wire eoe, eoi, eq;
   reg [3:0] a, b,c;

   neq_slice_es ees(eoe,abit,bbit,ei);
   neq_slice eis(eoi,abit,bbit,ei);
   nequal eqaul1(eq,a,b);

   integer   i, es_probs, ei_probs, eq_probs;
   reg       shadow_eo, shadow_eq;

   initial 
     begin
        es_probs = 0;
        ei_probs = 0;
        eq_probs = 0;

        for(i=0; i<8; i=i+1) 
          begin

             {abit,bbit,ei} = i[2:0];
             shadow_eo = ( abit != bbit ) && ei;

             #1;

             if( shadow_eo !== eoe ) 
               begin
                  if( !es_probs ) 
                    $display("Problem with eq_slice_es at a = %d, b = %d, ei = %d",
                             abit, bbit, ei);
                  es_probs = es_probs + 1;
               end

             if( shadow_eo !== eoi ) 
               begin
                  if( !ei_probs ) 
                    $display("Problem with eq_slice at a = %d, b = %d, ei = %d",
                             abit, bbit, ei);
                  ei_probs = ei_probs + 1;
               end
          end
        
        for(i=0; i<256; i=i+1) 
          begin

             {a,b} = i[7:0];
             shadow_eq = a ==~b;

             #1; 

             if( shadow_eq !== eq ) 
               begin
                  if( !ei_probs ) 
                    $display("Problem with not equal at a = %d, b = %d", a, b);
                  eq_probs = eq_probs + 1;
               end
             
          end
        
        $display("Done with tests.");
        if( eq_probs + es_probs + ei_probs == 0 ) $display("No problems found.");
     end
   
endmodule