Editing DOS/360 and successors (section)

===Utilities===
DOS/360 had a set of [[utility program]]s, an [[Assembly language|Assembler]], and [[compiler]]s for [[FORTRAN]], [[COBOL]] and eventually [[PL/I]], and it supported a range of file organizations with [[access method]]s to help in using them:

* Sequential data sets were only read or written, one record block at a time from beginning to end.
* In indexed ([[ISAM]]) files a specified section of each record was defined as a key which could be used to look up specific records.
* In direct access ([[basic direct access method|BDAM]]) files, the application program had to specify the physical location on the disk of the data it wanted to access. BDAM programming was not easy and most customers never used it themselves; but it was the fastest way to access data on disks and many software companies used it in their products, especially [[database management system]]s such as [[ADABAS]], [[IDMS]] and IBM's [[DBOMP]] and [[Data Language Interface|DL/I]].
Sequential and ISAM files could store either fixed-length or variable-length records, and all types could occupy more than one disk volume.