# Difference between Serial Adder and Parallel Adder

**1. Serial Adder:** A serial adder is used to add two binary numbers in serial form. The two binary numbers to be added serially are stored in two shift registers. The circuit adds one pair at a time with the help of one full adder. The carry output from the full adder is applied to a D flip-flop, the output of which is then used as a carry input for the next pair of significant bits. However, the sum bit S from the output of the full adder can be transferred into a third shift register.

**2. ****Parallel Adder****:** A parallel adder is a combinational digital circuit that adds two binary numbers in parallel form. It consists of full adders connected in cascade, with the output carry from each full adder connected to the input carry of the next full adder.

### Difference between Serial Adder and Parallel Adder:

S. No. | Parameters | Serial Adder | Parallel Adder |
---|---|---|---|

1. | Addition manner | It is used to add two binary numbers in serial form. | It is used to add two binary numbers in parallel form. |

2. | Type of Registers | A serial adder uses shift registers. | A parallel adder uses registers with parallel loads. |

3. | Requirement | It requires a single full adder. | It requires multiple full adders. |

4. | Usage of | A carry flip-flop is used in the serial adder. | Ripple carry adder is used in the parallel adder. |

5. | Circuit Type | A serial adder is a sequential circuit. | A parallel adder is a combinational circuit. |

6. | Propagation Delay | In serial adder, propagation delay is less. | In parallel adder, propagation delay is present from input carry to output carry. |

7. | Speed | The serial adder has a slow speed as compared to the parallel adder. | The parallel adder has fast speed as compared to the serial adder. |

8. | Addition process | The addition process is carried out bit by bit. Therefore, addition time relies on bit count. | The addition process is carried out simultaneously. That implies all bits sum up simultaneously. Therefore, time does not rely on bit count. |

9. | Requirement of Components | It necessitates fewer components. | It necessitates more components because of design complexity. |

10. | Number of Full Adders | The number of required full adders is fixed i.e. one. | The number of required full adders is equal to the number of bits in the binary number. |