How Do I Input and Output Data?

In the last chapter we dealt with the question of how data can be stored with the help of variables in such a way that we can work with them in the program. We now turn to the question of how we can bring data into the program from the outside (data input) and get it out of the program again (data output). This chapter discusses input and output via the console/terminal, graphical user interfaces (GUIs) as well as input from/output to files and databases.