CSE 459.22: Using pointers

I got a few questions about the use of pointers, hence this post.

I wrote a simple piece of code that uses pointers, char* etc.; try it out.

   int main() {
     char* Months[12]; // creates Months[0], ..., Months[11]; each of these
     // is a pointer; currently they are all uninitialized.
     Months[0] = new char[21]; // this allocates 21 bytes and stores the
         // address of the first byte in Months[0]
     Months[1] = new char[21]; // similar
     cin >> Months[0];  // Reads into the bytes starting at the one whose
       // address is in Months[0], the input characters
     cin >> Months[1];  // similar
     cout << Months[0] << "\n"; // outputs the characters starting with the
       // one whose address is in Months[0]; keeps going till the null byte.
     cout << Months[1] << "\n"; // similar
     delete [] Months[0]; // release the space pointed to by Months[0]
     delete [] Months[1]; // similar
     return 0;
I compiled it and ran it as follows:

   xi 121 > g++ t1.cpp
   xi 122 > a.out

The first two "jan" and "feb" lines were my input; the next two were
the output.   
Next, I added the line:  

   Months[0][1] = 0;   Months[1][1] = 0;

immediately following the second input command and compiled and ran
it again.  Here is what I got:

   xi 123 > g++ t1.cpp
   jxi 124 > a.out

See if you can explain why.