Memory models, FAT, interrupts, and the open-source continuation of the original PC OS.
Where FreeDOS achieves genuine binary compatibility with MS-DOS, where it deliberately diverges, and what that means for running real DOS software.
How DOS exposes its entire system call interface through the software interrupt mechanism, with INT 21h as the single most important entry point.
The practical ways people actually run FreeDOS in 2026 — from firmware-flashing USB sticks to full virtual machines — and how to pick the right one.
How FreeDOS distributes and installs software as discrete packages, and the tools used to manage them, decades before Linux package managers existed.
How character and block device drivers register with the DOS kernel through a standard request-header protocol, loaded declaratively from CONFIG.SYS.
A practical tour of FreeDOS batch scripting: variables, control flow, argument handling, and the quirks that differ from a modern shell.
How the File Allocation Table represents files as linked chains of clusters, and why that simple design has both strengths and hard limits.
DOS had no scheduler and no processes in the modern sense — so how did pop-up utilities, mouse drivers, and print spoolers run 'in the background'? By staying resident and hooking interrupts.
Why DOS memory is split into distinct regions with different rules, and how HIMEM.EXE and EMM386.EXE make more of it usable.
How a FreeDOS machine goes from the boot sector to a command prompt, and how CONFIG.SYS and AUTOEXEC.BAT configure everything along the way.