An indexed file is a

computer file A computer file is a computer resource for recording data in a computer storage device, primarily identified by its file name. Just as words can be written to paper, so can data be written to a computer file. Files can be shared with and trans ...

with an

index Index (or its plural form indices) may refer to: Arts, entertainment, and media Fictional entities * Index (''A Certain Magical Index''), a character in the light novel series ''A Certain Magical Index'' * The Index, an item on a Halo megastru ...

that allows easy

random access Random access (more precisely and more generally called direct access) is the ability to access an arbitrary element of a sequence in equal time or any datum from a population of addressable elements roughly as easily and efficiently as any othe ...

to any record given its file key. The key must be such that it uniquely identifies a record. If more than one index is present the other ones are called ''alternate indexes''. The indexes are created with the file and maintained by the system. IBM supports indexed files with the ''Indexed Sequential Access Method'' (

ISAM ISAM (an acronym for indexed sequential access method) is a method for creating, maintaining, and manipulating computer files of data so that records can be retrieved sequentially or randomly by one or more keys. Indexes of key fields are mainta ...

) on OS/360 and successors. IBM virtual storage operating systems added

VSAM Virtual Storage Access Method (VSAM) is an IBM DASD file storage access method, first used in the OS/VS1, OS/VS2 Release 1 (SVS) and Release 2 (MVS) operating systems, later used throughout the Multiple Virtual Storage (MVS) architecture and no ...

, which supports indexed files as Key Sequenced Data Sets (KSDS), with more options. Support for indexed files is built into

COBOL COBOL (; an acronym for "common business-oriented language") is a compiled English-like computer programming language designed for business use. It is an imperative, procedural and, since 2002, object-oriented language. COBOL is primarily u ...

and

PL/I PL/I (Programming Language One, pronounced and sometimes written PL/1) is a procedural, imperative computer programming language developed and published by IBM. It is designed for scientific, engineering, business and system programming. I ...

. Other languages with more limited I/O facilities such as C support indexed files through add-on packages in a runtime library such as C-ISAM. Some of

Digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals ** Digital camera, which captures and stores digital ...

's operating systems, such as

OpenVMS OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using Ope ...

, support indexed file I/O using the Record Management Services. In recent systems,

relational database A relational database is a (most commonly digital) database based on the relational model of data, as proposed by E. F. Codd in 1970. A system used to maintain relational databases is a relational database management system (RDBMS). Many relati ...

s are often used in place of indexed files.

Language support

The COBOL language supports indexed files with the following command in the FILE CONTROL section ORGANIZATION IS INDEXED IBM PL/I uses the file attribute ENVIRONMENT(INDEXED) or ENVIRONMENT(VSAM) to declare an indexed file.

Language support

See also

Inline citations