---
# Documentation: https://sourcethemes.com/academic/docs/managing-content/

title: "Bit magic in C (and C++)"
subtitle: ""
summary: "Tips and trick for embedded C/C++"
authors: []
tags: []
categories: []
date: 2020-06-13T19:01:19+02:00
lastmod: 2020-06-13T19:01:19+02:00
featured: false
draft: false

# Featured image
# To use, add an image named `featured.jpg/png` to your page's folder.
# Focal points: Smart, Center, TopLeft, Top, TopRight, Left, Right, BottomLeft, Bottom, BottomRight.
image:
  caption: ""
  focal_point: ""
  preview_only: false

# Projects (optional).
#   Associate this post with one or more of your projects.
#   Simply enter your project's folder or file name without extension.
#   E.g. `projects = ["internal-project"]` references `content/project/deep-learning/index.md`.
#   Otherwise, set `projects = []`.
projects: []
---

# Set a bit
```c
// Set one bit high at position "bit" in input and store to output
output = input | (1 << bit);
// Shorthand
variable |= (1 << bit);
// Multiple bits
variable |= (0b101 << bit);
```

# Clear a bit
```c
// Clear one bit high at position "bit" in input and store to output
output = input & ~(1 << bit);
// Shorthand
variable &= ~(1 << bit);
// Multiple bits
variable &= ~(0b101 << bit);

```

# Toggle a bit
```c
// Clear one bit high at position "bit" in input and store to output
output = x ^ (1 << bit);
// Shorthand
variable ^= (1 << bit);
// Multiple bits
variable ^= (0b101 << bit);
```

# Math
```c
// Division using bitshift
output = input >> 1; // Divide by 2
output = input >> 2; // Divide by 4
output = input >> 3; // Divide by 8
// Multiply using bitshifting
output = input << 1; // Multiply by 2
output = input << 2; // Multiply by 4
output = input << 3; // Multiply by 8
```

# Set X number of bits high.
```c
output = (0b1 << X) -1;
```

# Miscellaneous
```c
// Check if number is ODD
if( (num & 1) == 1) {};
// Flip signed integer
num = ~num + 1;
// Power of two
num > 0 && (num & (num - 1)) == 0;
```