9.1 File processing and unit records
Punched-card and early magnetic-file systems stored records but often required each application to know physical layouts and processing sequences.
9.2 Direct-access storage creates opportunity
Magnetic disks made online record retrieval and update practical, encouraging software that could manage relationships and access paths.
9.3 Integrated Data Store
Charles Bachman's IDS, developed at General Electric in the early 1960s, combined linked record structures, data descriptions, recovery and manipulation facilities. It is widely treated as an early production DBMS [1][2].
9.4 Hierarchical databases and IMS
IBM's IMS was created during the 1960s for complex bill-of-material and operational data. Released in 1968, it used hierarchical structures and a specialised data language [3].
9.5 CODASYL network model
The Database Task Group formalised navigational databases in which programs followed declared set relationships among records. This provided performance and explicit control at the cost of physical and structural dependence.
9.6 Codd's relational model
Codd's 1970 paper argued that users and applications should be protected from internal representation and proposed relations as the basis for large shared data banks [4].
9.7 System R
IBM's System R project tested relational design, high-level queries, shared updates, integrity, logging, recovery, views and authorisation [5][6].
9.8 SQL and optimisation
System R work developed SQL and cost-based access-path selection, transferring navigation choices from the application programmer to the optimiser [6][7].
9.9 Commercial relational systems
Relational products expanded in the late 1970s and 1980s. SQL became a dominant interface for enterprise data, though implementations diverged from pure relational theory.
9.10 Distributed and specialised databases
Databases later spread across machines and adopted object, document, graph, column-family and key-value models. The underlying problem remained managed shared persistent state under failure and concurrency.