In the preceding section, we discussed how two binary bits can be added and the addition of two binary bits with a carry. In practical situations it is required to add two data each containing more than one bit. Two binary numbers each of n bits can be added by means of a full adder circuit. Consider the example that two 4-bit binary numbers B ₄B ₃B ₂B ₁ and A ₄A ₃A ₂A ₁ are to be added with a carry input C ₁. This can be done by cascading four full adder circuits as shown in Figure 5.48. The least significant bits A ₁, B ₁, and C ₁ are added to the produce sum output S ₁ and carry output C ₂. Carry output C ₂ is then added to the next significant bits A ₂ and B ₂ producing sum output S ₂ and carry output C ₃. C ₃ is then added to A ₃ and B ₃ and so on. Thus finally producing the four-bit sum output S ₄S ₃S ₂S ₁ and final carry output Cout. Such type of four-bit binary adder is commercially available in an IC package.