A blacklist is a list of data that the program being created, should accept. All other data should be accepted by the program.

To make source code more maintainable, programmers should write their code with the following features:

What does 'SQL' stand for?

Input validation is when a system will check that the input meets certain criteria, to ensure that the data is in an acceptable form.

Whitelists are often more effective and secure than Blacklists.

As well as indentation, the code should be grouped together in logical blocks by splitting them up with blank lines.