MUMPS

MUMPS (Massachusetts General Hospital Utility Multi-Programming System) or alternatively M, is a general-purpose computer programming language that provides ACID (Atomic, Consistent, Isolated, and Durable) transaction processing. Its differentiating feature is its "built-in" database, enabling high-level access to disk storage using simple symbolic program variables and subscripted arrays, similar to the variables used by most languages to access main memory.

The M database is a key-value database engine optimized for high-throughput transaction processing. As such it is in the class of "schema-less", "schema-free," or NoSQL databases. Internally, M stores data in multidimensional hierarchical sparse arrays (also known as key-value nodes, sub-trees, or associative memory). Each array may have up to 32 subscripts, or dimensions. A scalar can be thought of as an array element with zero subscripts. Nodes with varying numbers of subscripts (including one node with no subscripts) can freely co-exist in the same array.