Setting Bits in C

In C programming, setting a bit is the process of setting a specific bit of a binary number to 1. This operation is crucial in various applications, including memory management, data processing, and hardware control.

In this article, we will learn how to set a bit at a given position in a binary number. We will also explore how to set multiple bits simultaneously.

How to Set a Bit in C?

Setting a bit means setting its value to 1. In C, we can set a given bit using the OR operator (|) combined with a bit mask. Below is the truth table of OR:

From the above table, we can infer that:

• By ORing a bit with 1, the given bit is set to 1.
• By ORing a bit with 0, the given bit remains unchanged.

Setting a Specific Bit in C

To set a specific bit in a number, you can use a bit mask with the OR operator. In that bitmask number, only the bit you want to set is set to 1, and all other bits are set to 0.

Example:

Input:
binary_number: 01100111
bit to set: 5th

Output:
binary_number: 01100111
mask_used: 00100000

Result: 103

Time Complexity: O(1)
Space Complexity: O(1)

Setting Multiple Bits in C

We can also set multiple bits by creating a mask with multiple bits set to 1. ORing the number with this mask will set all corresponding bits.

Example: Setting the 1st, 3rd, and 4th Bits

We can use the left shift operator to create a mask, but remember the 0-based indexing in the shifting.

Time Complexity : O(n), where n is the number of bits to be set.
Space Complexity : O(1)

Frequently Asked Questions (FAQs) on Setting Bits in C

What is a bit mask?

A bit mask is a binary number used to manipulate specific bits in another binary number. It is often used in bitwise operations.

What is the difference between setting and clearing a bit?

Setting a bit changes its value to 1, while clearing a bit changes its value to 0.

How do you create a bit mask?

You can create a bit mask by shifting 1 to the left by the desired number of positions using the left shift operator ( <<). For example, 1 << 3 creates a bit mask with the 4th bit set to 1.

Can you set multiple bits at once?

Yes, you can set multiple bits at once by combining multiple bit masks using the OR operator. For example, (1