stack function call problem

Question

i have a function called fun1(), which is used for recursion. I am confused regarding the first call to this fun(--n);. What it will do and how will my stack pop my functions after each function finishes?

void fun(int n)
{
    if(n>0)
    {
        fun(--n);
        printf("%d",n);
        fun(--n);
    }
}

My main function is as below:

    int a;
    a=3;
    fun(a);

I want to know the order of execution and what my stack will contain before, during, and after the function call of the first fun(--n).

Answer 1

It will print 0120

                                  (3->[2]->1)
                                       +   +
                                       |   |
                          +------------+   +-------+
                          |                        |
                         ({2}->[1]->0)           ({1}->[0]->-1)
                                +   +                        +
                                |   |                        |
                 +--------------+   +----+                   |
                 |                       |                   +
                 |                       |                  (X)
                 +                       +
                ({1}->[0]->-1)          (0->X)
                       +    +
                       |    |
          +------------+    |
          |                 |
          |                 |
          +                 +
         ({0}->X)          (X)

The above is a representation of the call tree. Read like this: The first number in the ( ) , wrapped in { } is the value which the function receives for one call, the next number following an arrow represents the value decreased by one and it is used to call again. The [ ] represents when returning it is printed. The last number in ( ) is the value which is used to the second call after the printf . An (X) represents that it is not able to get into the if block. At the end of each ( ) braces the function returns to the point where it originated from (follow the lines). Note the value gets printed after returning of the first call.