In a MUMPS context, this means that there is no requirement for sequential nodes to exist — codice_6 and codice_7 may be used without defining, allocating space for, or using any space for nodes 2 through 98. Indeed, one can even use floating-point numbers and strings (codice_8, codice_9, codice_10, etc.), where the subscript names have some meaning external to the program. The access function codice_11 returns the next defined key or subscript value, 3.3 in this example, so the program can readily manage the data. Subscripts are always returned (and usually stored) in sorted order. Given their sorting and naming features, it's not uncommon for subscripts and variable names to be used as data stores themselves, independent of any data stored at their locations. This feature is often used for database indexes. E.g., codice_12. The MUMPS term globals does not refer strictly to unscoped variables, as in the C tradition. MUMPS Globals are variables which are automatically and transparently stored on disk and persist beyond program, routine, or process completion. Globals are used exactly like ordinary variables, but with the caret character prefixed to the variable name. Modifying the earlier example as follows:  SET ^A("first_name")="Bob" SET ^A("last_name")="Dobbs"   results in creation of a new disk record, which is immediately inserted within the file structure of the disk. It is persistent, just as a file persists in most operating systems. Globals are stored in structured data files by MUMPS, and accessed only as MUMPS globals. MUMPS has a long history of cached, journaled, and balanced B-tree key/value disk storage, including transaction control for multiple file transaction 'commit' and 'roll-back' at the language/operating system level. Real-world databases can often grow unpredictably (such as having 20 patients with a last name of 'Anderson' before you get any with surnames starting with 'B'), but modern MUMPS implementations are designed to structure the database efficiently as it grows. For all of these reasons, one of the most common MUMPS applications is database management. MUMPS provides the classic ACID properties as part of any standard MUMPS implementation. FileMan is an example of a DBMS built with MUMPS. The InterSystems Caché implementation allows dual views of selected data structures—as MUMPS globals, or as SQL data—and has SQL built in (called M/SQL).