If you're looking for a "good paper" or a technical explanation of how works, especially concerning file "building" or "rebuilding," here are the key technical concepts often covered in software analysis or whitepapers on download acceleration. How IDM "Builds" Files
IDM's ability to resume broken downloads by keeping track of which segments were completed before an interruption. Where to Find Official Info and Updates
The time it takes to "build" the file depends on your hard drive speed (SSD vs. HDD) and the file size, as the software is physically moving and joining gigabytes of data on your disk. Common Technical Topics for Research
For a competitive analysis, you might look at how IDM compares to Free Download Manager or Xtreme Download Manager , which use similar segmentation tech.
Ant Commander Pro file manager.