> For the complete documentation index, see [llms.txt](https://hkust-robotics-team.gitbook.io/hkust-robotics-team-software-tutorial/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hkust-robotics-team.gitbook.io/hkust-robotics-team-software-tutorial/tutorial/tutorial-1-c-and-cubeide-setup/advanced-c/enum.md).

# Enum

## Enumeration

**Enumeration** (aka Enum): User-defined data type for assigning names to constants, so the code becomes more legible.

> We will use `UPPER_SNAKE_CASE` most of the time for enums.

```c
enum week {
    SUNDAY, 
    MONDAY, 
    TUESDAY, 
    WEDNESDAY, 
    THURSDAY, 
    FRIDAY, 
    SATURDAY
};
/**
 * SUNDAY corresponds to 0
 * MONDAY corresponds to 1
 * ...
 * SATURDAY corresponds to 6
 * /
```

#### Sample Code

```c
#include <stdio.h> 

enum week {
    SUNDAY, 
    MONDAY = 0, 
    TUESDAY = 3
};
  
int main() { 
   printf("%d, %d, %d\n", sunday, monday, tuesday); 
   return 0; 
}
```

Output:

```
0, 0, 3
```

You can also declare enum variables.

```c
// creating an enum variable called `day` of type `week`

enum week {
    SUNDAY, 
    MONDAY, 
    TUESDAY
} day;

/*--- OR ---*/

enum week {
    SUNDAY, 
    MONDAY, 
    TUESDAY
};
enum week day;
```

#### Sample Code

```c
#include <stdio.h> 
  
enum week {
    SUNDAY, 
    MONDAY = 3, 
    TUESDAY
}; 
  
int main() { 
    enum week day; 
    day = tuesday; 
    printf("%d\n", day); 
    return 0;
}
```

Output:

```
4
```

Enums are useful when we want to define multiple variables which can be grouped together.