英文“sure”和“of course”用法有什么不同?

sure 是很爽块地回答可以,一定,无疑的.
of course 是理所当然的意思.
两者很多情况下能混用.
举例,必须用sure的时候:
He is clever,to be sure,but not very hard-working.
She is sure to pass the examination.
必须用 of course的时候:
Mothers as a matter of course have much affection for their children.
I will write to you of course,but not every week.