UNIT 1 - Present Continuous (I am doing)

a) We use the present continuous when we talk about which is happening at the time of speaking:

   ~ Please don't make so much noise. I'm studying. (not 'I study')

   ~ 'Where is Margaret?'   'She's having a bath.' (not she has')

   ~ Let's go out ow. It isn't raining any more.

   ~ (at the party) Hello, Ann. Are you enjoying the party? (not 'do you enjoy')

b) We also use the present continuous when we talk about something which is happening around the time of speaking, but not necessarily exactly at the time of speaking. Study this example situation:

   ~ Tom and Ann are talking and drinking in a cafe. Tom says: ' I'm reading an interesting book at the moment. I'll lend it to you when I've finished it.'

Tom is not reading the book at the time of speaking. He means that he has begun the book and hasn't finished it yet. He is in the middle of reading it. Here are some more examples:

   ~ Silvia is learning English at the moment. (not 'learns')

   ~ Have you heard about Tom? He is building his own house. (not 'build')

But perhaps Silvia and Tom are not doing these things exactly at the time of speaking.

c) We often use the present continuous when we talk about a period the present. For example: today, this season, etc.:

   ~ ' You're working hard today.'  'Yes, I have a lot to do'

   ~ Tom isn't playing football this season. He wants to concentrate on his studies.

d) We use the present continuous when we talk about changing situations:

   ~ The population of the world is rising very fast. (not 'rises')

   ~ Is your English getting better? (not 'does ... get')

Thank's to Cambridge University Press, "English Grammar in Use"