帮我写一篇英语作文,要求无语法错误,语句通畅,不少于80词,

Computer is a kind of useful invention in the world. Much work has been done on computers so they are convenient and useful . We can do many things on them .We can find some information , watch plays ,play games and also shop on them .But on the other hand they afftecs people's life. Because some people are spending too much time on them ,which surely affects their work or study.So I think we should use them properly.