C++ float array initialization

Possible Duplicate:
C and C++ : Partial initialization of automatic structure

While reading Code Complete, I came across an C++ array initialization example:

float studentGrades[ MAX_STUDENTS ] = { 0.0 };

I did not know C++ could initialize the entire array, so I've tested it:

#include <iostream>
using namespace std;

int main() {
    const int MAX_STUDENTS=4;
    float studentGrades[ MAX_STUDENTS ] = { 0.0 };
    for (int i=0; i<MAX_STUDENTS; i++) {
        cout << i << " " << studentGrades[i] << '\n';
    }
    return 0;
}

The program gave the expected results:

0 0
1 0
2 0
3 0

But changing the initialization value from 0.0 to, say, 9.9:

float studentGrades[ MAX_STUDENTS ] = { 9.9 };

Gave the interesting result:

0 9.9
1 0
2 0
3 0

Does the initialization declaration set only the first element in the array?