Basics

- const char vs char
  `const char *p`: This declares a pointer p that points to a constant character (immutable). It means that the data pointed to by p cannot be modified through p. However, p itself can be changed to point to a different memory location.
  So `p[0]='H'` is invalid as this constant say 'hello' is read only
   but if it is simply `char *p` then `p[0]='H'` is a valid operation
    
   **Wierd Case**
   if 
`const char *p` is equivalent to 'hello' and we do 
`char *q=p;`
and 
`q[0]='H'`
then it is invalid bcz constant pointed by p is still read only and no matter if another pointer is pointing to it, that constant is still read only.