Recently I just finished my semester exams and used this website mainly to study. It has detailed, concise and precise information about almost every topic in computer science. It explains concepts right from the basics and with easy to understand language which can be read and interpreted by anyone , even someone who has just started their syllabus.
I had used it before during my sessional examinations and just used it to revise some topics. It hardly took me about 30 minutes to catch up faster than ever. After that which I studied other new topics from this website. They also have well explained numerical problems which eased my troubles even more.
Moreover it also has some extra information which is helpful for short answer questions.
I would recommend to use thid website if you are in a hurry and can not open a text book and start reading in between the lines. There is only one disadvantage with this website is that some content on this website is paid content and can not be accessed. But nevertheless it is a must option if your in a hurry.