Verilog HDL Program for Serial Parallel Multiplier

module spm(s,m,q);
output [7:0]s;
input [3:0]m,q;
and1 u1(s[0],m[0],q[0]);
and1 u2(s1,m[0],q[1]);
and1 u3(s2,m[0],q[2]);
and1 u4(s3,m[0],q[3]);
and1 u5(s4,m[1],q[0]);
and1 u6(s5,m[1],q[1]);
and1 u7(s6,m[1],q[2]);
and1 u8(s7,m[1],q[3]);
and1 u9(s8,m[2],q[0]);
and1 u10(s9,m[2],q[1]);
and1 u11(s10,m[2],q[2]);
and1 u12(s11,m[2],q[3]);
and1 u13(s12,m[3],q[0]);
and1 u14(s13,m[3],q[1]);
and1 u15(s14,m[3],q[2]);
and1 u16(s15,m[3],q[3]);
parad4 u21({s18,s17,s16,s[1]},c3,{s7,s6,s5,s4},{1'b0,s3,s2,s1});
parad4 u22({s21,s20,s19,s[2]},c7,{c3,s18,s17,s16},{s11,s10,s9,s8});
parad4 u23({s[6],s[5],s[4],s[3]},s[7],{c7,s21,s20,s19},{s15,s14,s13,s12});
endmodule
 
module parad4(a,c,p,q); // Parallel Adder Module
output [3:0]a;     output c;     input [3:0]p,q;    wire c1,c2,c3;
ha u1(a[0],c1,p[0],q[0]);
fa u2(a[1],c2,p[1],q[1],c1);
fa u3(a[2],c3,p[2],q[2],c2);
fa u4(a[3],c,p[3],q[3],c3);
endmodule