A typical computer has many registers, and we need to transfer the information between these registers. A way to transfer the information is using the common bus system. The construction of this bus system for 4 registers is shown above. The bus consists of 4×1 multiplexers with 4 inputs and 1 output and 4 registers with bits numbered 0 to 3. There are 2 select inputs S0 and S1 which are connected to the select inputs of the multiplexers. The output 1 of register A is connected to input 0 of MUX 1 and similarly other connections are made as shown in the diagram. The data transferred to the bus depends upon the select lines.