The answer lies in the company policy so would change....
To give you a general idea based on the hew HR Manuals that I've gone through as of yet -
If an employee is under probation, the employer/employee can terminate the employment with immediate notice with/out reason...
However if the performance is not upto mark, employer reserves the right to terminate the employee with/out notice.
If termination is caused on misconduct, there is no notice and this reason/misconduct is stated on the letter which would be like a red remark for him/her.
Hope it helped.
6th December 2012 From India, Mumbai