Software or computer programs are written in a particular computer language (a human readable code), which is called source code. If your source code is original, it can be protected under copyright. Copyright protection is not only valid for the code itself, but also for interfaces, flowcharts, and aesthetic elements such as icons, etc.
However, keep in mind that copyright only protects the literal text, not the technology described by the code. This implies that others can produce the same digital product or service, as long as they come up with their own code.
Copyright protection does not require any registration. You obtain protection automatically as of the date you created the software. Without registration it can be difficult to prove the official creation date of your software development. There are different ways you can prove the creation date of your software: e.g. you can record the source code in an i-DEPOT or you can use online version control systems (this keeps track of who created what and when). A copyright has a lifespan of 70 years after the death of the author.