Most file systems that support hard links use reference counting. The system stores an integer value with each logical data section that represents the total number of hard links that have been created to point to the data. When a new link is created, this value is increased by one. When a link is removed, the value is decreased by one. When the counter becomes zero, the operating system frees the logical data section. (The OS may not to do so immediately, e.g., when there are outstanding file handles open, for performance reasons, or to enable the undelete command.)