PRESENT PROGRESSIVE (CONTINUOUS)
The present progressive expresses an activity that is in progress at the moment of speaking. It began in the recent past, is continuing at present, and will probably end at some point in the future.
a. John is sleeping right now.
k. I need an umbrella because it is raining.
l. John and Marry are talking on the phone.
Often the activity is of a general nature : something generally in progress this week, this month, this year.
Note (o) : The sentence means that writing a book is a general activity she is engaged in at present, but it does not mean that at the moment of speaking she is sitting at her desk with pen in hand.
m. I am taking five courses this semester.
n. John is trying to improve his work habits.
o. She is writing another book this year.