There was a technique that used a thing called overlays[0]. You could write a program that is much larger than the available address space (64k on MS/PCDOS) but

There was a technique that used a thing called overlays[0]. You could write a program that is much larger than the available address space (64k on MS/PCDOS) but you split it up into functional areas or modules that are loaded on demand into a reserved area of your 64k address space. [0]: https://en.wikipedia.org/wiki/Overlay_(programming) https://en.wikipedia.org/wiki/Overlay_(programming)