What are non- printable characters , these are invisible characters that you can still see on the document!
Non-printable characters are also often referred to as control characters, but some are also special characters . Non-printable characters are used to perform certain formatting / control actions, for example line breaks, tabs, page breaks. Or these are just invisible like tabs, spaces, ....!
Non-printable characters can also cause problems because they are not visible, in most programs you can display non-printable characters such as page breaks , but non-printable characters are also very important in documents, websites, ... !