File descriptor

A nonnegative integer identifying an open access in one operating-system process. The program passes its value to operations such as reading and closing; the operating-system kernel interprets it through that operating-system process's descriptor table. In the toy example, table entry 3 refers to an open file description for inode 42. Another operating-system process's entry 3 can reach a different file, and a closed file descriptor value can be reused. ^[ref]