 Welcome to our guide to computer science. One of the main reasons that we've created this guide is that although computers are a big part of our lives and in the world all around us, a lot of people don't really understand what computer science is. I was going to take computer science but I basically already know how to use word in Excel. And it is one of those things that you don't really notice until it's missing. For example, then you end up with things like really slow programs. Or incredibly frustrating interfaces. Or systems that can't cope with large amounts of data. And these days a business can become a thousand times bigger overnight. That's exactly when you need it to be able to cope with a lot of data. We look at topics like computer security to make sure that any personal information you're holding can't be accessed by hackers. Or artificial intelligence for planning and decision making. Computer graphics for entertainment and also visualizing large amounts of data. And computer vision where computer can sense objects and even people in the world around it. We look at computer programs that take so long to run that they won't finish in a lifetime even on the fastest computer. We'll think about what it means for a computer to be intelligent and we'll look at how compression works so that we can take thousands of songs and fit them on a device that's small enough to fit in your pocket. Computer science has many things to many people and after working through this guide you'll have a better idea of what computer science is and especially how we can use it to design software that will help people in their everyday lives.