半加器
      s = a xor b
     c = a and b
      半加器、全加器、串行进位加法器、并行进位加法器
 
 
 全加器
      si = ai xor bi xor Ci-1
      Ci = (ai xor bi) and Ci-1 or  (ai and bi)
      半加器、全加器、串行进位加法器、并行进位加法器
 
 
串行进位加法器
     半加器、全加器、串行进位加法器、并行进位加法器

 
并行进位加法器（超前进位加法器）
     进位生成项 Gi = Ai and Bi
     进位递归条件 Pi = Ai xor Bi
     进位表达式 Ci=(Ai and Bi) or ((Ai xor Bi) and Ci-1)
                  = Gi or (Pi and Ci-1)

     和表达式 Si = Ai xor Bi xor Ci = Pi xor Ci-1

     递推公式:

        S0 = P0 xor C0-1

        C0 = G0 or (P0 and C0-1)

        S1 = P1 xor C0

        C1 = G1 or (P1 and C0)

           = G1 or (P1 and G0) or (P1 and P0 and C0-1)

        S2 = P2 xor C1

        C2 = G2 or (P2 and C1)

           = G2 or (P2 and G1) or (P2 and P1 and G0) or

             (P2 and P1 and P0 and C0-1)

        S3 = P3 xor C2

        C3 = G3 or (P3 and C2)

           = G3 or (P3 and G2) or (P3 and P2 and G1) or

              (P3 and P2 and P1 and G0) or

              (P3 and P2 and P1 and P0 and C0-1)