What's the difference between these senstences?

Question

1: He did not have a pen.

2: He does not have a pen.

3: He did not had a pen.

Answer 1

1st one is past tense

2nd one is present tense

3rd one is incorrect 

Answer 2

1: He did not have a pen.

**This one is past tense. If you expand it a bit, you will see what I mean.

- When he went in to the exam room that morning, to his dismay he found that he did not have a pen. 

2: He does not have a pen.

**Ths one is present tense. 

- Could someone help out Jared? He does not have a pen.

3: He did not had a pen.

**This one is incorrect. You cannot have did not and had together in the same sentence. 

Answer 3

When you make a sentence into a question, a negative, or an emphatic, you only have ONE ending to indicate tense. 

He had a pen. (the past tense ending is on "had")

He did not have a pen (the past tense ending moves to "did" and comes off "have")

Did he have a pen? 

He did have a pen-- I saw it! (emphatic)

The same is true for the 3rd person singular present tense ending.

He has a pen (the third person "s" is on "has")

He does not have a pen (the third person "s" move to "do" and comes off "have")

Does he have a pan? 

He does have a pen but he refuses to use it. (emphatic)

Answer 4

1. simple past tense

2. simple present tense

3. totally incorrect -- you can't follow "did" with the simple past "had"

correct:  He did not HAVE a pen.

Answer 5

1 is the past. 2 is the present. 3 is grammatically incorrect.

Answer 6

1. It's simple past-tense. The action of him not having a pen is in the past and complete. Being in the past, he could have a pen now.

2. It's present tense. The action of him not having a pen is in the present and is not complete.

3. This sentence is grammatically incorrect. The complete verb "did had" is an ungrammatical construction because it improperly uses the past tense of the auxiliary verb "did" with the past tense of "had" when only the bare infinitive "have" can be used after "did," a "bare infinitive" being an infinitive without "to." That's because the grammatical construction is an auxiliary verb followed by a bare infinitive (i.e., aux. verb + bare infinitive).