EASTER EGGS

For various reasons, ranging from a simple game to the desire to leave something personal inside a digital object, programmers have always introduced small portions of software into the various programs that are not related to the object that contains them. Generally they are neither evident nor declared.
Easter eggs are hidden not only in strictly so-called software programs, but also in products such as electronic games and DVD films, which in any case have components that can be traced back to the structure of the software.
Often they are very simple, almost trivial objects, such as the list of names of those who participated in the project, other times they are fairly elaborate and complex programs (such as the flight simulator in Microsoft Excel 97), in the case of films in DVD these are hidden scenes or messages from the director for whoever finds them. The way to discover these curious Easter Eggs is not simple, sometimes random, there is no universal system, you have to search and try in a thousand different ways, often having knowledge of the facts.
There are many sites dedicated to the study and enumeration of Easter Eggs often divided into categories and themes, sites where you can find the instructions for reaching the individual surprises.
We don't want to make a list of individual Easter Eggs here, which are a huge number in constant obvious expansion, but a rundown of the sites that talk about them.

The phenomenon is amusing and funny, but it gives the starting point for a reflection on the content, at least of the software: if one knows that there is hidden and undeclared software, but ultimately known in some way, what on earth can one hide that still don't know?