# What is recursion in C?

When a function calls itself, and this process is known as recursion. The function that calls itself is known as a recursive function.

Recursive function comes in two phases:

- Winding phase
- Unwinding phase

**Winding phase**: When the recursive function calls itself, and this phase ends when the condition is reached.

**Unwinding phase**: Unwinding phase starts when the condition is reached, and the control returns to the original call.

**Example of recursion**

```
int calculate_fact(int);
int main()
{
int n=5,f;
f=calculate_fact(n); // calling a function
printf(“factorial of a number is %d”,f);
return 0;
}
int calculate_fact(int a)
{
if(a==1)
{
return 1;
}
else
return a*calculate_fact(a-1); //calling a function recursively.
}
```

**Output:**

factorial of a number is 120

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