Legal drinking age. The legal drinking age is the age at which a person can legally consume or purchase alcoholic beverages. These laws cover a wide range of issues and behaviors, addressing when and where alcohol can be consumed.
An open system is a system that has external interactions. Such interactions can take the form of information, energy, or material transfers into or out of the system boundary, depending on the discipline which defines the concept.
Open source refers to any application for which you can see and change the underlying code. A big advantage of an open source program is that it is a collaborative between many people. If there is a problem, many people will see the problem and work on a solution. Linux is an example of an open source operating system.