Emphatic Forms of the Verb -- American English

The emphatic forms of a verb are often used to give greater emphasis to the idea express by the verb. The auxiliaries do, does and did are used to give this additional emphasis. The emphatic forms are used in only two tenses, the present tense and the past tense.

Emphatic Form Present Tense
Person Singular Plural
First Person I do call We do call
Second Person You do call You do call
Third Person He, she, it does call They do call
 
Emphatic Form Past Tense
Person Singular Plural
First Person I did call We did call
Second Person You did call You did call
Third Person He, she, it did call They did call

When do, does, and did are used in questions, the form is not for emphasis. The use of do, does, and did in questions is an idiomatic way of asking questions in English. In the following questions do, does, and did are not the emphatic form of the verb.

Do you have to go now?
Does he want to eat tonight?
Did she buy that hat this week?

Also when do, does, and did are used to mean accomplish, carry out, etc., the form is not used for emphasis in these cases. Here are examples of that:

I do my homework after class.
He does a good job every day.
We did our best work today.