Why this array overflow happening in c

Question

https://code.sololearn.com/cZFDbih9YA6C/?ref=app

Answer 1

U declared a[10] it usually means 10 contiguous memory blocks to store 10 integers but Because u tried to access the value at memory location that wasn't allocated...... results are unpredictable when u do this

Answer 2

Sometimes it gives error like segmentation fault or may give garbage value