The difference between "past continuous" and "present perfect continuous"

Question

Let's consider the following context:

You come to the office on Saturday and see somebody finish some actions and now (s)he is sitting at your workplace (you didn't expect to meet anyone), but anyway you are not surprised and just want to know what's happened.

There are at least two ways to ask your colleague:

• What were you doing here?

• What have you been doing here?

According to the rules I've learned, there is no big difference between these options.

Of course, our choice could depend on what my colleague is doing when I ask or other rules I don't know, but I do want to know what native speaker feels comparing these two questions in the above context and what the difference is.

Answer 1

In the case of the present perfect continuous, the action is still going on, but you consider the past portion of it. Example: Your colleague is on your computer doing something and you ask: ''What have you been doing here''?

In the case of the past progressive, the action was going on in the past. Example: Your colleague is sitting on your workplace. He turned off the computer and was about to leave when you arrived and asked: ''What were you doing here?''

In the case of the present progressive, as you indicated it in the title, the action is going on in the present/right now. Example: Your colleague is doing something on your computer and you ask: ''What are you doing here?''

So, the answer depends on what your colleague is doing at the moment you ask this question and what portion of time you consider.

Answer 2

The past continuous tense is used to describe an action that began in the past and ended in the past.

The present perfect continuous is used to describe an action that began in the past but continues up till the point of speaking about it(the present).

Considering the scenario that you've provided, if you reached your workplace and noticed that your colleague is still at work, you might ask, "What have you been doing?"

If you notice that your colleague is no longer working, but is chilling out, you have to use the past continuous form and ask, "What were you doing?"

This summary chart clearly explains the different tenses and their usages.

Answer 3

For me, as a native English speaker, I would say "What are you doing here?" meaning "Why are you here?". This would apply whether the person was actually performing a task or not. I might say the same thing to an unexpected visitor to my home. If the colleague said "I've been sorting something out" I might ask "What have you been doing?" in the sense of "Tell me what you've done in more detail". Hope this helps.