Storing and using data with variables

We can think of a variable as a named storage box. We choose a name, perhaps variableA. These names are like our programmer's window into the memory of the user's Android device.

Variables are values in memory ready to be used or altered when necessary by using their name.

Computer memory has a highly complex system of addressing that, fortunately, we do not need to interact with. Java variables allow us to devise our own convenient names for all the data we need our program to work with. The DVM will handle all the technicalities to interact with the operating system and the operating system will in turn interact with the physical memory.

So, we can think of our Android device's memory as a huge warehouse just waiting for us to add our variables to it. When we assign names to our variables, they are stored in the warehouse ready for when we need them. When we use our variable's name, the device knows exactly what we are referring to. We can then tell...