The most useful invention is computer. It is changing our life. Computer is an important part in our ***.It is our ***.It makes our life more and more convenient.Doctors need computers to look over patient's illness.Teachers need computer to teach students.We also need computer to study our subjects.If we feel tired,we can listen to the music in the computer. Computers also makes our world a big family because we can communitate with people from other countries on the internet. We can send and receive emails to our friends in a second.