Label

Label is an 8-byte, 32-bit word pair variable consisting of a 4-byte text address and a 4-byte frame pointer value. The text address identifies the first instruction of a labeled statement in the containing procedure. The frame pointer value identifies the address of the stack frame of the block containing the statement. Label values can be assigned, compared for equality or inequality, passed as arguments, and returned from functions. No calculations or conversions can be performed on them, and they cannot be transmitted in stream I/O.