One of the most important logical operations in Boolean algebra and various electronic devices is the OR operation. Numerous Integrated Circuits (ICs) use this concept in real life. Although these circuits use logical gates, the input and output depend on the same logic.
The Logical OR operation is based on fundamental concepts that can be learned by examining the truth table below. Before looking at the OR operation truth table, it’s important to know the sign used in this type of operation. In the Boolean OR operation, the sign used is (+). Now, let’s examine the inputs and outputs of the truth table.
| Input (A) | Input (B) | Output (Y) |
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
This truth table displays two inputs and a single output. When inputs A and B are set to 0, the output is also 0. When A is set to 0 and B to 1, the output is 1. Similarly, when A is set to 1 and B to 0, the output is 1. Finally, when A and B are set to 1, the Logical OR operation output is also 1.
In a logical OR operation, the output is only 0 when both inputs are 0. If either input is 1, the output is 1. This logic can be applied in digital circuits. In these circuits, 1 represents the flow of a signal pulse, while 0 represents the flow of no signal. To better understand the concept of Boolean OR operation, you can follow the switch circuit diagram shown in Figure below.
In the diagram above, there are two switches connected in parallel. As I mentioned earlier, 1 indicates the signal flow in this circuit, while 0 indicates no signal flow. If either of the switches is closed, there will be an output. However, if both switches are open, there will be no output. This logic is equivalent to the Logical OR operation. When S1 and S2 are both 0, the output is also 0. However, if either S1 or S2 is closed (set to 1) or both are closed, the output will have a signal pulse, which is equivalent to the OR operation.
Binary logic is similar to binary arithmetic, where the OR Operation is like addition, and the AND operation is like multiplication. Although the symbols used for OR and AND operations are the same as those used for arithmetic variable addition and multiplication, it’s important to distinguish between a binary arithmetic variable and a logic variable. A binary arithmetic variable can consist of one or more digits, while a logic variable always consists of only one digit, either 0 or 1. In binary arithmetic, 1 + 1 equals 10. In binary logic, 1 + 1 equals 1.