Memory models, FAT, interrupts, and the open-source continuation of the original PC OS.
You edited CONFIG.SYS, rebooted, and now the system hangs or won't load drivers correctly. Here's how to get back to a bootable state without reinstalling.
The single most common reason to boot FreeDOS today: building a bootable USB stick to run a vendor's DOS-based firmware update tool.
Getting a CD-ROM drive recognized and assigned a drive letter on FreeDOS through the driver-plus-MSCDEX layering DOS CD-ROM support was always built on.
Installing a text editor and a couple of common utilities on FreeDOS, and wiring them into your PATH and environment correctly.
Creating a primary partition, an extended partition with logical drives, and setting the active boot partition the way DOS disks have always been organized.
Installing FreeDOS onto a virtual machine or real hardware, from booting the installer through to a working CONFIG.SYS and AUTOEXEC.BAT.
Getting real TCP/IP networking working on FreeDOS using mTCP and a packet driver, enough for FTP, Telnet, and a basic text-based browser.
A register-level guide to the interrupt vector table, FreeDOS INT 21h dispatch, file and process calls, Carry Flag errors, BIOS services, TSR hooks, and reentrancy.
A source-backed guide to FreeDOS conventional memory, UMBs, the HMA, XMS and EMS, with safe Jemm and Himem configuration and troubleshooting practices.
FreeDOS 1.2 shipped December 25, 2016 with the new FDI installer, FDIMPLES package selection, multiple USB and CD images, and a much broader software catalog.