Present Perfect Continuous : ( Structure –  Subject + has been/ have been  + verb + ing) This tense denotes an action begun some time in the past and still continuing at the time of speaking.  In this tense, we can mention the length of time involved in the action.  But, this is not possible in the case of Present Continuous Tense.

Comparison of present perfect continuous and present continuous.

• They have been studying in the government school since 2001.( This is present perfect continuous- the time involved in the action is clearly mentioned)
• They are studying in the government school.(This is present continuous – here we cannot indicate the length of time involved in the action.
• How long have you been working in the garden?
• We have been working in the garden for two hours.
• I have been reading this book since the morning.
• His hands are dirty.  He has been repairing the car.( it doesn’t matter whether the repairing has been finished or not)
• It’s nice to see you again.  What have you been doing since we last met.