Access control.

When specific means are used to limit access or entry to a place or system, those means are a form of access control. Access control is typically used to ensure privacy and security. It has taken many different forms over the years and has gone from being primarily physical in the early twentieth century to mostly digital in the early twenty-first century (for example, computer privacy). While a business may be protected by a gate and a safe by a combination lock, an email address is protected by a password, and data stored by a business is protected by software. These examples of access control are different ways to achieve the same privacy and security objective, adapted to different situations.