1. An algorithm used in constructing and maintaining hashed random files by which record keys are modified to produce their addresses in the address space of the file (on magnetic disc). A variety of algorithms are used, either singly or in combination; for example, folding, truncation, dividing by a constant and taking either the quotient or remainder, changing the radix, and squaring. Extraction (by mask) is often used to obtain an address of the required number of digits and various methods are used to select an output that is within the address space of the file.