PPT Slide
“Ancient” Memory Sharing Techniques
- Overlays: older technique that placed the burden of loading/unloading pieces of a program based on evaluating the subroutine/function usage patterns.
- Allowed programs that were larger than physical memory to run!
- Lot of effort to create the “overlay tree”, though.
- Figure 11.19 is an example.
- DOS overlays are a special case of how maintaining an old design (the 640K PC) really muddied the memory management waters of newer PCs for years (Figure 11.20’s plethora of memory styles is mind-numbing).