In C all functions except main() can be called recursively.

#include<stdio.h>
#include<stdlib.h>

int main()
{
    int i=0;
    i++;
    if(i<=5)
    {
        printf("CuriousTab");
        exit(1);
        main();
    }
    return 0;
}

#include<stdio.h>
int check(int);
int main()
{
    int i=45, c;
    c = check(i);
    printf("%d\n", c);
    return 0;
}
int check(int ch)
{
    if(ch >= 45)
        return 100;
    else
        return 10;
}

#include<stdio.h>
int check (int, int);

int main()
{
    int c;
    c = check(10, 20);
    printf("c=%d\n", c);
    return 0;
}
int check(int i, int j)
{
    int *p, *q;
    p=&i;
    q=&j;
    i>=45? return(*p): return(*q);
}

#include<stdio.h>
void fun(int);
typedef int (*pf) (int, int);
int proc(pf, int, int);

int main()
{
    int a=3;
    fun(a);
    return 0;
}
void fun(int n)
{
    if(n > 0)
    {
        fun(--n);
        printf("%d,", n);
        fun(--n);
    }
}

#include<stdio.h>
int fun(int);
int main()
{
    float k=3;
    fun(k=fun(fun(k)));
    printf("%f\n", k);
    return 0;
}
int fun(int i)
{
    i++;
    return i;
}