Why does the value go out of index of the array?

Question

In bubble sort, when first iteration of the inner for loop takes place, value of i is 0 , so the loop will run till j is less than n , but when j becomes equal to n-1 , and we do a[j+1] for another time.
why doesn't this value go out of index of the array and the code executes properly?

    for(i=0;i<n-1;i++) {
        for(j=0;j<n-i;j++) {        /* When i=0 & j<n why doesn't  */
            if(a[j] > a[j+1]) {     /* a[j+1] go out of index when */
                temp=a[j+1];        /* value of j is n-1           */
                a[j+1]=a[j];
                a[j]=temp;
            }
        }
    }

Answer 1

Well this is a proper , Tested Bubble Sort function:

void bubble_sort(long a[], long n)
{
  long i, j, t;

  for (i = 0 ; c < ( n - 1 ); i++)
  {
    for (j = 0 ; j < n - i - 1; j++)
    {
      if (a[j] > a[j+1])
      {
        t         = a[j];
        a[j]   = a[j+1];
        a[j+1] = t;
      }
    }
  }
}

Answer 2

I think the problem is with you second for's, second argument. It should run till j is less than i , not n .

void bubble(double *t, int db) {
    int i, j;
    for (i = db-1; i > 0; --i)
        for (j = 0; j < i; ++j)
            if (t[j+1] < t[j]) {
                double temp = t[j];
                t[j] = t[j+1];
                t[j+1] = temp;
            }
}