Why this happen

Question

I still dont understand when you add a new value to an index witch doesnt exist and wher this four come for last line
I want an explication fir this 3 and for and why not 9 ?
https://code.sololearn.com/coQM5xI6uHqg/?ref=app

Answer 1

thats due to buffer overflow, which will generate a garbage value, you're accessing beyond the array bound.

to get your desired output set t[4] and assign t[4] =9;

Answer 2

How to set a new index to be able to pit smth on