Memory models, FAT, interrupts, and the open-source continuation of the original PC OS.https://danielcosenza.com/en-usThu, 16 Jul 2026 00:00:00 GMThttps://danielcosenza.com/posts/dos-fix-corrupt-mbr/https://danielcosenza.com/posts/dos-fix-corrupt-mbr/A non-destructive FreeDOS recovery sequence for imaging the disk, auditing partitions and active flags, repairing boot code, and verifying files.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSmbrbootrecoveryhttps://danielcosenza.com/posts/dos-fix-fast-games/https://danielcosenza.com/posts/dos-fix-fast-games/How to identify CPU-bound timing loops and choose throttling, cache, emulator-cycle, or period-correct hardware solutions without damaging the installation.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSgamestimingtroubleshootinghttps://danielcosenza.com/posts/dos-fix-fat-corruption/https://danielcosenza.com/posts/dos-fix-fat-corruption/How to image first, distinguish media failure from filesystem damage, and use CHKDSK-style repair only after preserving evidence.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSfatcorruptionrecoveryhttps://danielcosenza.com/posts/dos-fix-himem-emm386-conflict/https://danielcosenza.com/posts/dos-fix-himem-emm386-conflict/Diagnose FreeDOS HIMEM and EMM386 conflicts with a controlled boot menu that isolates XMS, EMS, UMB, ROM exclusions, and driver order.Sun, 12 Jul 2026 00:00:00 GMTFreeDOShimememm386memoryhttps://danielcosenza.com/posts/dos-fix-keyboard-codepage/https://danielcosenza.com/posts/dos-fix-keyboard-codepage/Fix FreeDOS keyboard and codepage mismatches by separating scan-code mapping from display glyphs and aligning COUNTRY, KEYB, MODE, and fonts.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSkeyboardcodepagelocalizationhttps://danielcosenza.com/posts/dos-howto-archive-files/https://danielcosenza.com/posts/dos-howto-archive-files/Choose ZIP or 7-Zip workflows deliberately, verify archives, and bridge 8.3 names, long filenames, codepages, and modern storage.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSarchiveszipbackuphttps://danielcosenza.com/posts/dos-howto-freecom-advanced-batch/https://danielcosenza.com/posts/dos-howto-freecom-advanced-batch/Build reusable FreeCOM batch routines with arguments, labels, error handling, controlled environments, safe temporary files, and predictable quoting.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSfreecombatchscriptinghttps://danielcosenza.com/posts/dos-howto-legacy-print-server/https://danielcosenza.com/posts/dos-howto-legacy-print-server/Capture LPT output safely, preserve control codes, and choose raw or converted queues without pretending every DOS printer stream is plain text.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSprintinglptlegacyhttps://danielcosenza.com/posts/dos-howto-multiboot-menu/https://danielcosenza.com/posts/dos-howto-multiboot-menu/Build a safe FreeDOS multiboot menu with FDCONFIG.SYS sections and matching FDAUTO.BAT branches for gaming, networking, diagnostics, and recovery.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSmultibootconfig-sysrecoveryhttps://danielcosenza.com/posts/dos-howto-serial-link/https://danielcosenza.com/posts/dos-howto-serial-link/Build a reliable FreeDOS serial link by validating UART settings, null-modem wiring, flow control, terminal configuration, and file checksums.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSserialnull-modemtransferhttps://danielcosenza.com/posts/dos-howto-test-monthly-release/https://danielcosenza.com/posts/dos-howto-test-monthly-release/Test a FreeDOS monthly release safely by verifying media, cloning the environment, comparing package changes, capturing regressions, and reporting evidence.Sun, 12 Jul 2026 00:00:00 GMTFreeDOStestingmonthly-releaseqahttps://danielcosenza.com/posts/dos-news-floppy-edition-14/https://danielcosenza.com/posts/dos-news-floppy-edition-14/FreeDOS 1.4's separate floppy installer ships 720 KiB, 1.2 MiB and 1.44 MiB image sets for classic PCs, with a reduced package set and no bundled source.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSfloppyinstallerretro-hardwarehttps://danielcosenza.com/posts/dos-news-microweb-21/https://danielcosenza.com/posts/dos-news-microweb-21/MicroWeb 2.1 shipped March 12, 2026 with XMS support, simple downloads and lower memory use while retaining its HTTP-only, no-CSS, no-JavaScript design.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSmicrowebbrowserxmshttps://danielcosenza.com/posts/dos-news-monthly-test-releases/https://danielcosenza.com/posts/dos-news-monthly-test-releases/Since 2022, FreeDOS Tyymm test releases have assembled packages and installers monthly, enabling continuous integration testing before stable releases.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSrelease-engineeringtestingdistributionhttps://danielcosenza.com/posts/dos-news-t2603-new-kernel/https://danielcosenza.com/posts/dos-news-t2603-new-kernel/FreeDOS highlighted kernel 2044 and Windows 3.x testing in T2603 in March 2026, although the kernel first entered the monthly distribution in February's T2602.Sun, 12 Jul 2026 00:00:00 GMTFreeDOSkernelwindows-3xtestinghttps://danielcosenza.com/posts/dos-com-vs-exe-loading/https://danielcosenza.com/posts/dos-com-vs-exe-loading/Two genuinely different DOS executable formats, with real structural differences in how each loads into memory and why COM files had a strict 64K limit.Sat, 11 Jul 2026 00:00:00 GMTFreeDOScom-filesexe-formatprogram-loadinghttps://danielcosenza.com/posts/dos-command-com-internals/https://danielcosenza.com/posts/dos-command-com-internals/The clever reload-from-disk trick that let DOS's COMMAND.COM recover automatically after a large program overwrote its expendable transient portion.Sat, 11 Jul 2026 00:00:00 GMTFreeDOScommand-comshelldos-architecturehttps://danielcosenza.com/posts/dos-fix-usb-drive-not-detected/https://danielcosenza.com/posts/dos-fix-usb-drive-not-detected/Getting a USB flash drive to appear as a drive letter under FreeDOS by correctly configuring USBASPI's driver chain, or falling back to BIOS-level access.Sat, 11 Jul 2026 00:00:00 GMTFreeDOSfixusbhardwarehttps://danielcosenza.com/posts/dos-freedos-kernel-architecture/https://danielcosenza.com/posts/dos-freedos-kernel-architecture/FreeDOS's kernel is a from-scratch, clean-room reimplementation, and its authors' actual architecture choices differ deliberately from how MS-DOS was built.Sat, 11 Jul 2026 00:00:00 GMTFreeDOSfreedos-kernelarchitecturedos-chttps://danielcosenza.com/posts/dos-howto-dev-environment/https://danielcosenza.com/posts/dos-howto-dev-environment/Installing a C compiler and assembler on FreeDOS and building your first program, for anyone wanting to write DOS software rather than just run it.Sat, 11 Jul 2026 00:00:00 GMTFreeDOShowtodevelopmentopen-watcomfreedoshttps://danielcosenza.com/posts/dos-howto-doslfn-setup/https://danielcosenza.com/posts/dos-howto-doslfn-setup/Installing DOSLFN, understanding what it can and can't do, and verifying long filenames actually work with your specific FreeDOS utilities.Sat, 11 Jul 2026 00:00:00 GMTFreeDOShowtodoslfnfilenameshttps://danielcosenza.com/posts/dos-howto-play-classic-games/https://danielcosenza.com/posts/dos-howto-play-classic-games/Getting sound, mouse, and memory configured correctly for DOS-era gaming — the three things almost every classic game setup guide assumes already work.Sat, 11 Jul 2026 00:00:00 GMTFreeDOShowtogamingsound-blasterfreedoshttps://danielcosenza.com/posts/dos-howto-ramdisk-setup/https://danielcosenza.com/posts/dos-howto-ramdisk-setup/Configuring a RAM disk with the built-in RAM driver — a fast, volatile drive letter backed by memory, useful for temporary files and disk-heavy tasks.Sat, 11 Jul 2026 00:00:00 GMTFreeDOShowtoramdiskmemoryhttps://danielcosenza.com/posts/dos-howto-tsr-batch-menu/https://danielcosenza.com/posts/dos-howto-tsr-batch-menu/Building a batch-file boot menu that manages memory-hungry TSRs — loading only what a chosen task needs, freeing conventional memory for everything else.Sat, 11 Jul 2026 00:00:00 GMTFreeDOShowtobatch-filestsrmemoryhttps://danielcosenza.com/posts/dos-howto-usb-drive-setup/https://danielcosenza.com/posts/dos-howto-usb-drive-setup/Configuring the USBASPI/ASPIDISK driver chain to give FreeDOS a working drive letter for a USB flash drive, bridging DOS-era drivers to a newer standard.Sat, 11 Jul 2026 00:00:00 GMTFreeDOShowtousbusbaspihardwarehttps://danielcosenza.com/posts/dos-news-11-release/https://danielcosenza.com/posts/dos-news-11-release/FreeDOS 1.1 arrived January 2, 2012 with kernel 2040, mTCP, initial UHCI USB support and UIDE, while its official notes documented installer limits.Sat, 11 Jul 2026 00:00:00 GMTFreeDOSnewsfreedosreleasehttps://danielcosenza.com/posts/dos-news-14-release/https://danielcosenza.com/posts/dos-news-14-release/FreeDOS 1.4 shipped April 5, 2025 with FreeCOM 0.86, FDISK and mTCP fixes, reorganized media, monthly-test-release input, and the proven 1.3 kernel.Sat, 11 Jul 2026 00:00:00 GMTFreeDOSnewsfreedosreleasehttps://danielcosenza.com/posts/dos-news-freedos-25th-anniversary/https://danielcosenza.com/posts/dos-news-freedos-25th-anniversary/FreeDOS marked 25 years on June 29, 2019 with Jim Hall's account of PD-DOS, early utilities, community-built FreeCOM and kernel work, and three stable releases.Sat, 11 Jul 2026 00:00:00 GMTFreeDOSnewsfreedosanniversaryhttps://danielcosenza.com/posts/dos-news-msdos-end-of-support/https://danielcosenza.com/posts/dos-news-msdos-end-of-support/Microsoft's archived table records December 31, 2001 as DOS support retirement, but its surviving row names MS-DOS 6.0 rather than 6.22.Sat, 11 Jul 2026 00:00:00 GMTFreeDOSnewsms-dosend-of-lifehttps://danielcosenza.com/posts/dos-news-pd-dos-announcement/https://danielcosenza.com/posts/dos-news-pd-dos-announcement/Jim Hall's June 29, 1994 Usenet post proposed PD-DOS with a manifest and task list; contributors responded, and the GPL project became Free-DOS within weeks.Sat, 11 Jul 2026 00:00:00 GMTFreeDOSnewsfreedosjim-hallhistoryhttps://danielcosenza.com/posts/dos-umb-tsr-loading-high/https://danielcosenza.com/posts/dos-umb-tsr-loading-high/How DOS users reclaimed conventional memory by relocating drivers and TSRs into unused upper memory gaps, which varied by machine and BIOS.Sat, 11 Jul 2026 00:00:00 GMTFreeDOSumbtsrmemory-optimizationhttps://danielcosenza.com/posts/dos-xms-ems-memory/https://danielcosenza.com/posts/dos-xms-ems-memory/Why DOS ended up with three separate, incompatible ways to access memory beyond the conventional 640K barrier, and what each one was actually solving.Sat, 11 Jul 2026 00:00:00 GMTFreeDOSxmsemsmemory-managementhttps://danielcosenza.com/posts/dos-fix-doslfn-issues/https://danielcosenza.com/posts/dos-fix-doslfn-issues/Why long filenames appear truncated in some programs but not others even with DOSLFN loaded, and how to tell which behavior is actually expected.Fri, 10 Jul 2026 00:00:00 GMTFreeDOSfixdoslfnfilenameshttps://danielcosenza.com/posts/dos-fix-rtc-datetime-issues/https://danielcosenza.com/posts/dos-fix-rtc-datetime-issues/How to distinguish a dying CMOS battery from a software configuration issue when FreeDOS boots with the wrong date or time every session.Fri, 10 Jul 2026 00:00:00 GMTFreeDOSfixrtcdate-timehttps://danielcosenza.com/posts/dos-news-10-release/https://danielcosenza.com/posts/dos-news-10-release/FreeDOS 1.0 arrived September 3, 2006 with installable base and full distributions, a boot floppy, package tools, source media, and a LiveCD option.Fri, 10 Jul 2026 00:00:00 GMTFreeDOSnewsreleasefreedoshttps://danielcosenza.com/posts/dos-news-13-release/https://danielcosenza.com/posts/dos-news-13-release/FreeDOS 1.3 arrived February 20, 2022 with kernel 2043, FreeCOM 0.85a, an 8086 FAT32 build, restored networking, compressed floppy media, and installer fixes.Fri, 10 Jul 2026 00:00:00 GMTFreeDOSnewsreleasefreedoshttps://danielcosenza.com/posts/dos-batch-files/https://danielcosenza.com/posts/dos-batch-files/A FreeCOM-specific guide to portable DOS batch files using arguments, SHIFT, IF, ERRORLEVEL, FOR, GOTO, CALL, redirection, and defensive expansion.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSbatch-filesscriptingfreedoshttps://danielcosenza.com/posts/dos-boot/https://danielcosenza.com/posts/dos-boot/A forensic walkthrough of FreeDOS startup from BIOS, MBR and volume boot code through KERNEL.SYS, FDCONFIG.SYS, FreeCOM, FDAUTO.BAT, drivers, and recovery keys.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSbootconfig-sysfreedoshttps://danielcosenza.com/posts/dos-device-drivers/https://danielcosenza.com/posts/dos-device-drivers/A source-backed tour of FreeDOS device headers, character and block drivers, request packets, entry points, INIT, status words, and loading risks.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSdevice-driverskernelfreedoshttps://danielcosenza.com/posts/dos-fat-filesystem/https://danielcosenza.com/posts/dos-fat-filesystem/A forensic guide to FreeDOS FAT12, FAT16 and FAT32 layout, cluster typing, directory and VFAT entries, allocation chains, mirrors, corruption, and recovery.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSfatfilesystemfreedoshttps://danielcosenza.com/posts/dos-fix-bad-command/https://danielcosenza.com/posts/dos-fix-bad-command/Distinguish a typo from a missing PATH entry, a wrong file extension, or a corrupted COMMAND.COM behind FreeDOS's generic error message.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSfixcommand-linetroubleshootinghttps://danielcosenza.com/posts/dos-fix-irq-conflicts/https://danielcosenza.com/posts/dos-fix-irq-conflicts/Diagnosing why a sound, network, or serial device fails or hangs the system when used alongside another — classic IRQ conflicts and how to resolve them.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSfixhardwarefreedoshttps://danielcosenza.com/posts/dos-fix-out-of-environment-space/https://danielcosenza.com/posts/dos-fix-out-of-environment-space/SET commands or a long PATH suddenly fail with 'Out of environment space.' The environment block has a fixed size, and here's how to actually fix it.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSfixconfig-sysfreedoshttps://danielcosenza.com/posts/dos-fix-printer-lpt/https://danielcosenza.com/posts/dos-fix-printer-lpt/A DOS program can't print, or output is garbled — usually a port configuration, IRQ, or cable-mode mismatch, all diagnosable without any special tools.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSfixprinterlpthardwarehttps://danielcosenza.com/posts/dos-fix-soundblaster-config/https://danielcosenza.com/posts/dos-fix-soundblaster-config/Diagnosing missing or wrong DOS game audio by tracing the BLASTER environment variable against the card's actual jumper or Plug-and-Play settings.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSfixsound-blasteraudiohardwarehttps://danielcosenza.com/posts/dos-fix-wont-boot-config-sys/https://danielcosenza.com/posts/dos-fix-wont-boot-config-sys/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.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSfixconfig-sysbootfreedoshttps://danielcosenza.com/posts/dos-howto-bootable-usb-flashing/https://danielcosenza.com/posts/dos-howto-bootable-usb-flashing/The single most common reason to boot FreeDOS today: building a bootable USB stick to run a vendor's DOS-based firmware update tool.Thu, 09 Jul 2026 00:00:00 GMTFreeDOShowtofirmwareusbfreedoshttps://danielcosenza.com/posts/dos-howto-cdrom-mscdex/https://danielcosenza.com/posts/dos-howto-cdrom-mscdex/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.Thu, 09 Jul 2026 00:00:00 GMTFreeDOShowtocdrommscdexfreedoshttps://danielcosenza.com/posts/dos-howto-edit-applications/https://danielcosenza.com/posts/dos-howto-edit-applications/Installing a text editor and a couple of common utilities on FreeDOS, and wiring them into your PATH and environment correctly.Thu, 09 Jul 2026 00:00:00 GMTFreeDOShowtoapplicationsfreedoshttps://danielcosenza.com/posts/dos-howto-fdisk-partition/https://danielcosenza.com/posts/dos-howto-fdisk-partition/Creating a primary partition, an extended partition with logical drives, and setting the active boot partition the way DOS disks have always been organized.Thu, 09 Jul 2026 00:00:00 GMTFreeDOShowtofdiskpartitioningfreedoshttps://danielcosenza.com/posts/dos-howto-install/https://danielcosenza.com/posts/dos-howto-install/Installing FreeDOS onto a virtual machine or real hardware, from booting the installer through to a working CONFIG.SYS and AUTOEXEC.BAT.Thu, 09 Jul 2026 00:00:00 GMTFreeDOShowtoinstallfreedoshttps://danielcosenza.com/posts/dos-howto-mtcp-networking/https://danielcosenza.com/posts/dos-howto-mtcp-networking/Getting real TCP/IP networking working on FreeDOS using mTCP and a packet driver, enough for FTP, Telnet, and a basic text-based browser.Thu, 09 Jul 2026 00:00:00 GMTFreeDOShowtonetworkingmtcpfreedoshttps://danielcosenza.com/posts/dos-interrupts/https://danielcosenza.com/posts/dos-interrupts/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.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSinterruptsdos-apifreedoshttps://danielcosenza.com/posts/dos-memory/https://danielcosenza.com/posts/dos-memory/A source-backed guide to FreeDOS conventional memory, UMBs, the HMA, XMS and EMS, with safe Jemm and Himem configuration and troubleshooting practices.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSmemoryfreedosdoshttps://danielcosenza.com/posts/dos-news-12-release/https://danielcosenza.com/posts/dos-news-12-release/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.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSnewsreleasefreedoshttps://danielcosenza.com/posts/dos-news-msdos-opensource/https://danielcosenza.com/posts/dos-news-msdos-opensource/On September 28, 2018, Microsoft placed MS-DOS 1.25 and 2.0 source and binaries on GitHub under MIT; MS-DOS 4.00 followed separately in April 2024.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSnewsms-dosopen-sourcehttps://danielcosenza.com/posts/dos-package-mgmt/https://danielcosenza.com/posts/dos-package-mgmt/A verified guide to FreeDOS ZIP packages, FDIMPLES, FDINST and FDNPKG, including real commands, metadata, local media, repositories, updates, and trust risks.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSpackage-managementfreedoshttps://danielcosenza.com/posts/dos-running-today/https://danielcosenza.com/posts/dos-running-today/A practical 2026 guide to running FreeDOS 1.4 in QEMU, virtual machines, emulators or real hardware, with verified boot, USB, firmware and network safety advice.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSfreedosvirtualizationsysadminhttps://danielcosenza.com/posts/dos-tsr-programs/https://danielcosenza.com/posts/dos-tsr-programs/A forensic guide to DOS TSR residency, interrupt hooks, chaining, INT 28h and InDOS reentrancy, multiplex IDs, memory ownership, safe unloading, and testing.Thu, 09 Jul 2026 00:00:00 GMTFreeDOStsrfreedosdosinterruptshttps://danielcosenza.com/posts/dos-vs-msdos/https://danielcosenza.com/posts/dos-vs-msdos/A precise comparison of FreeDOS and MS-DOS across APIs, executables, kernels, shells, filesystems, hardware, licensing, undocumented behavior, and testing.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSfreedosms-doscompatibilityhttps://danielcosenza.com/posts/dos-what-is/https://danielcosenza.com/posts/dos-what-is/The history, goals, and real-world use cases behind FreeDOS, the open-source, actively-maintained continuation of the MS-DOS-compatible operating system line.Thu, 09 Jul 2026 00:00:00 GMTFreeDOSfreedoshistorydos