Some early ATMs might have been effectively green screen terminals calling into CICS or IMS interface. These days it's more likely that the COBOL is somewhere

Some early ATMs might have been effectively green screen terminals calling into CICS or IMS interface. These days it's more likely that the COBOL is somewhere in the IMS transactions (IBM bragged sometime in last decade that ~80% of ATM transactions are implemented on top of IMS at some point). IMS is a navigational (CODASYL) database system with iirc a form of application server - what you'd call today a NoSQL database :P - designed for Apollo project supply chain handling.