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.
An operating system is the software you install on your computer that allows you to operate the computer. Windows is an operating system. If you want to find out what operating system you have then this is very simple.