To clarify, that's a text file. We ran batch programs overnight to process claims and create billing reports (this is fake data, but I consulted on insurance an

To clarify, that's a text file. We ran batch programs overnight to process claims and create billing reports (this is fake data, but I consulted on insurance and legal systems back in the mid-eighties). That batch program was modular and would run several "passes" over the file (sequentially) to do varying types of work (create new data, create reports). These programs could also change a record if they needed to. A claims record might have a status indicator like "submitted" (S), "billed" (B), "denied" (D), "paid" (P). Everyone that writes code today works on the shoulders of such systems and some of these systems still exist (social security, hotel reservations, flight scheduling, banking, insurance) all original designed by IBM. Most of these have Java and DB2 layers on top of them now, but the underlying data is in many cases still there. The modularization was because 32mb that had to be split up to handle varying functionality (procedural BASIC or C). There would be a MAIN module, then any number of sub-modules and you'd describe how they would swap in and out as needed. (See PDP-11/RSTS-E Task Builder). Relational databases were magic when we started using them in the early nineties. NOSql databases are also magic. Graph databases are pure wizardry.