In security, specifically location security, the term access control refers first to the practice of restricting entrance to a facility or property to authorized persons, and secondly to the mechanisms which keep track of entries and exits (i.e. visitor's logs, security cameras) or prevent access by unauthorized persons (i.e. gates, electronic locks, biometrics).

Computer security implements access control by passwords, physical devices including biometric scans and metal locks, hidden paths, digital signatures, encryption, social barriers, audit trails, and monitoring by humans and automated systems.

In telecommunication, the term access control has the following meanings:

1. A service feature or technique used to permit or deny use of the components of a communication system.
2. A technique used to define or restrict the rights of individuals or application programs to obtain data from, or place data onto, a storage device.
3. The definition or restriction of the rights of individuals or application programs to obtain data from, or place data into, a storage device. There are several types of access control; for example Role Based Access Control (RBAC), Mandatory Access Control (MAC), and Discretionary Access Control (DAC).
4. [The] process of limiting access to the resources of an AIS to authorized users, programs, processes, or other systems.
5. That function performed by the resource controller that allocates system resources to satisfy user requests.

Sources:

• U.S. Federal Standard 1037C
• U.S. MIL-STD-188
• U.S. National Information Systems Security Glossary