Sometimes it’s useful, or even necessary, to change the value type of a variable and use it for other purposes. For instance, if you had a double with a percent score on a test, say 0.95, you would most likely want to display 95% to the user instead. Notice, we are not changing the type of the variable, nor the value stored in the source variable. What we are doing is displaying the changed variable as a new type or storing it in a different variable that might be a different type.

So you could not do this:

int a;
double b = 3.0;
a = b;

There are two types of conversions, implicit and explicit. When you set one variable to be the same as another, such as a = b above, but their types do not match, the compiler will try to convert them. However, this can be dangerous as you might not know what values will be in the variable at runtime, and it might not be implicitly convertible to another type. Our example above was implicit, the compiler in this case will make a best guess.

The other way to convert a variable from another type is explicitly. You can do this by simply telling the compiler what type you want to set it to. So in our example above we could change the line a = b to a = (int)b. That way if b was something other than 3.0, such as 3.2, we are telling the compiler to make it work, so it would set it to 3.