**COMBINATIONAL CIRCUITS**

*This article is going to be in parts because it is going to be a broad course. This course will contain the simulations of all the digital circuits that will be taught.*

**Arithmetic Circuits**
Arithmetic circuits are circuits that performs arithmetic operations on binary numbers. In a computer, these operations are performed in the arithmetic and logic unit (ALU). This is a part of the central processing unit (CPU) of a computer. The ALU is responsible for performing two operations; the arithmetic and logic operations.

The arithmetic operations includes; Addition, Subtraction, Multiplication(process of repeated additions) and Division(process of repeated subtraction); while the logic operations include AND, OR, NAND, NOR, NOT .etc.

The fundamental building blocks that forms all hardware used to perform all the arithmetic operations on binary numbers mentioned above includes; Full adder, Half adder, Full subtractor, Half subtractor and Controlled inverter.

**Half Adder**
It can be said to be the arithmetic circuit block that can be used to add two bits (which are called the inputs) to produce to outputs; the sum and the carry outputs.

The truth table for the half adder can be seen below;

A |
B |
Sum |
Carry |

0 |
0 |
0 |
0 |

0 |
1 |
1 |
0 |

1 |
0 |
1 |
0 |

1 |
1 |
0 |
1 |

fig .1. Truth table of the half adder

fig .2.block symbol of the half adder

The circuit diagram of the half adder can drawn from the equation which can be gotten from the truth table above;

fig .3.

As can be seen in the picture above, the sum of the half adder can either be obtained by using the NOT, AND and the NOR gates or simply using the EXOR gate. While the carry can simply be realised by using the AND gate.

The circuit of the half adder can be seen below;

The complete video on how to simulate this will be available soon, please comment below if you have any questions.

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