Punctuation

Full stop or period (.)

• To mark the end of a positive/negative statement, the end of  a complete thought, as in:
• Their little son is learning to walk.
•  I still don't understand it.
•  To mark the end of initials or abbreviation; sometimes it is optional, as in:
• p.m. and a.m.
• R.I.P or RIP
• Mr. and Mrs. 

Question Mark (?) 

• To signal that a message or an utterance is in direct question form, as in: 
• Is pink your favorite color?
• Why not?
• To show doubt/unsure about something.

o    (?)……..   Doubtful of a sentence, as in:

          (?) She seems a selfish girl.

o    (?)……...  Doubtful of information, as in:

          In December 1980 (?), John Lennon was shot dead. 

Comma (,) 

• To separate a series of items from the same categories: 
• We are looking forward to buy shirt, shoes, trousers, and skirts
• To separate a transitional expression:
• By the way, what do you think about my new clothes?
• To be used after subordinate or dependent clause that precedes a main or independent clause:
• If i know you better, I will not miss-understand you.
• To introduce a verb phrase beginning with 'to':
• To succeed in studies, we have to be studious.
• To add non defining phrase or clause or a comment clause to a sentence:
• Their uncle, a farmer, plants onion in Riau.
• To introduce adverb of frequency, place, and time at the beginning of a sentence:  
• Sometimes, the students just waste their time gossiping.