 Consider this program which calculates a person's approximate age and days. There's nothing wrong with it. It works great when we compile it and when we run it. It says that someone who's 21 years old is about 7,665 days old. However, these variable names Y and D aren't particularly good. If we had a very long program with lots of variables, we might not know instantly what D stands for. Days, discount, deposit, or what? You should always make your variable names as meaningful as possible. In this program, changing Y to years and D to days makes the program much more readable with a minimum of effort. Suppose we wanted to be a bit more specific and rename the variables as age in years and age in days. We could rename age in years as A-I-Y and age in days as A-I-D, but that would be a terrible idea. First, A-I-Y is meaningless, and second, A-I-D sounds more like a call for help than an age. When we spell out the name entirely, we get names that are long and difficult to read. How then do we handle multi-word variable names? One solution is to use underscores between the words of the variable name. This is called snake case because the underscores make the word look sort of like the segments of a snake's body. Another method, which is the one that is used by convention in Java, is camel case, where each word after the first is capitalized. It's called camel case because the capital letters are reminiscent of the humps of a camel, if you use a lot of imagination. In this course, we'll expect you to use camel case for all your multi-word variable names. Guys, always use meaningful variable names. Don't make them too short. Don't make them ridiculously long. Make them meaningful and just the right size.