Question: What is the difference caused by using “nope” instead of ”no”?

Is it used because “nope” sounds better and not straight like “no”? In some situations, it feels like *nope* is better to use than *no* even though it adds 2 more characters. What is the reason why many use it?

Answer: 
From [here](https://english.stackexchange.com/a/59658/31820), they have no difference in meaning; but *nope* is more informal, only used in a sense of opposite to *yes* (or *yup*). Also, *nope* is not used often in writing.

You wouldn't say "there were nope errors", for example.
'Nope' is a variant of 'no' (exclamation). 

First known use: 1888 ([M-W](https://www.merriam-webster.com/dictionary/nope#h1))

Phonologically, pronunciation can explain where the P came from.

Suppose someone asked you a question and you said 'No'. You'd usually pause after saying 'No' (exclamation) with your lips already positioned to articulate a P, that's why most people articulate a P. That's called *excrescent P*. (Sometimes producing a little puff of air is for emphasising 'no' while leaving it unreleased indicates lazy and sloppy speech.)