There are multiple problems in this code:
printf("%d", i); has undefined behavior.
The prototype for main without arguments is int main(void). Defining main as void main() is non portable and incorrect on some platforms. Always use the Standard prototypes for main and return a valid exit status for good style.
It is bad style to call the main function recursively in C, and it has undefined behavior in C++.
Ignoring the fact that undefined behavior means anything can happen, including Indian firms using horrendous programming tests, the reason the program prints 0000 is you probably mistyped the if (i--) test or misplaced the braces from memory, or the guy is plain wrong. The main function calls itself recursively 3 times decrementing the same i variable each time until it becomes 0 and each instance prints the value of i, namely 0 before it returns to its caller, including the initial invocation of main().
static int i = 4; inside a function defines a global variable i with an initial value of 4 that can only be accessed inside the block where it is defined. All recursive instances of main access the same variable.
