C :: Variable Length Array - Core Dumps

This code snippet compiles and runs fine

Code:
#include <stdio.h>

int main(void) {
int i, a[i];

i=2;
for(int n=0; n<=i; n++)
a[n]=0;

[Code] .....

It prints out 3 "0", but when slightly changed

Code:
#include <stdio.h>
int main(void) {
int i, a[i];

i=200;
for(int n=0; n<=i; n++)

[Code] ....

It compiles fine but core dumps when run, how come? i'm using gcc version 4.4.7, and compiling like this

gcc -std=c99 test.c -o test