--- title: BMAGIC url: 'https://wiki.teletypegames.org/dos/bmagic' markdown: 'https://wiki.teletypegames.org/dos/bmagic.md' lang: en date: '2026-10-13' description: 'Boot Magic (BMAGIC.EXE) is a DOS program (C++, Open Watcom, 16-bit, about 64 KB) that edits the boot menu of MS-DOS 6 and later. It reads CONFIG.SYS, AUTOEXEC.BAT and MSDOS.SYS in the root folder of the boot drive, maps the menu in them, and lets you add, edit, copy, rename, move and delete menu i…' taxonomy: tag: - howto --- # BMAGIC > Boot Magic (`BMAGIC.EXE`) is a DOS program (C++, Open Watcom, 16-bit, about 64 KB) that edits the boot menu of MS-DOS 6 and later. It reads `CONFIG.SYS`, `AUTOEXEC.BAT` and `MSDOS.SYS` in the root folder of the boot drive, maps the menu in them, and lets you add, edit, copy, rename, move and delete menu items, edit their lines, and set the default item, the timeout, the colors and NumLock. It also sets the startup options of a Windows 95/98 `MSDOS.SYS`. > > It changes only the lines it has to change. Before every save it shows the changes in a diff and backs up the files; any backup can be compared with the files on the disk or restored. It is built in layers on [DOSLIB](https://wiki.teletypegames.org/dos/doslib), like [GMENU](https://wiki.teletypegames.org/dos/gmenu) and [DOSINST](https://wiki.teletypegames.org/dos/dosinst). - **Repository:** [git.teletypegames.org/dos/bmagic](https://git.teletypegames.org/dos/bmagic) - **Download v0.1.0:** [BMAGIC-v0.1.0.zip](https://git.teletypegames.org/dos/bmagic/releases/download/v0.1.0/BMAGIC-v0.1.0.zip) · the executable alone: [BMAGIC.EXE](https://git.teletypegames.org/dos/bmagic/releases/download/v0.1.0/BMAGIC.EXE) - **Releases:** [git.teletypegames.org/dos/bmagic/releases](https://git.teletypegames.org/dos/bmagic/releases) ![Boot Magic on a drive without a boot menu](https://wiki.teletypegames.org/wiki-assets/bmagic/bmagic-menu.png) # Installation - **With DOSINST:** `DOSINST INSTALL BMAGIC` installs the latest release from the [DOSINST](https://wiki.teletypegames.org/dos/dosinst) store to `C:\APPS\BMAGIC`, and running it again updates it. An update keeps the backups (DOSINST keeps files it did not install); `DOSINST REMOVE BMAGIC` deletes the folder, the backups too. - **By hand:** copy `BMAGIC.EXE` to any folder, for example `C:\APPS\BMAGIC\`. ``` BMAGIC the boot files of the boot drive BMAGIC D: the boot files of another drive (for example a disk you prepare) ``` The boot drive comes from DOS (4.0 and later); if DOS cannot tell, Boot Magic uses `C:`. In DOSBox give the drive (`BMAGIC C:`), because DOSBox does not boot from these files. The exit code is 0 when files were written, 1 when nothing was written, and 2 on an error. Restart the computer after saving: DOS reads these files only at boot. # The boot menu ``` CONFIG.SYS AUTOEXEC.BAT [MENU] @ECHO OFF MENUITEM=NORMAL,Normal start PATH C:\DOS <- every configuration MENUITEM=GAMES,Games (EMS) GOTO %CONFIG% MENUDEFAULT=NORMAL,10 :NORMAL MENUCOLOR=15,1 LH SMARTDRV NUMLOCK=OFF GOTO END :GAMES [COMMON] LH MOUSE DOS=HIGH,UMB <- every item GOTO END :END [NORMAL] DEVICE=C:\DOS\HIMEM.SYS [GAMES] DEVICE=C:\DOS\HIMEM.SYS DEVICE=C:\DOS\EMM386.EXE RAM ``` An item is a `MENUITEM` line of `[MENU]`, a `[NAME]` block in `CONFIG.SYS`, and a section of `AUTOEXEC.BAT` from the `:NAME` label to the next label. DOS sets `CONFIG` to the name of the chosen item, and `GOTO %CONFIG%` jumps to its label. The sections end with a `GOTO` to a common end label (`:END` unless the file uses another one). | Action | Key | What changes | |---|---|---| | New item | Ins | A `MENUITEM` line after the last one, a `[NAME]` block after the last item block, a section before the end label ending with `GOTO END`. It can be a copy of another item. The first item of a `CONFIG.SYS` without a menu creates `[MENU]`, and the lines already there go under `[COMMON]`. | | Rename | F3 | The `MENUITEM` line, the `[NAME]` line, `MENUDEFAULT`, the `INCLUDE=NAME` lines and the `:NAME` label. | | Delete | Del, then Y | The `MENUITEM` line, the block, the section, `MENUDEFAULT` and the `INCLUDE` lines. Deleting the last item also removes `[MENU]` and `GOTO %CONFIG%`. | | Move | Ctrl+PgUp / Ctrl+PgDn | Swaps two `MENUITEM` lines, the order of the menu. | | Menu | F6, F5 | `MENUDEFAULT` (item and 0-90 s timeout), `MENUCOLOR`, `NUMLOCK`; F5 makes the selected item the default. | | Lines | Enter, F8 | The block and section of an item, or a whole file (Tab moves to the next one). Lines are edited up to 200 characters. | | MSDOS.SYS | F7 | `BootMenu`, `BootMenuDefault`, `BootMenuDelay`, `BootGUI`, `Logo`, `BootKeys` in the `[Options]` block of a Windows 95/98 `MSDOS.SYS`; its attributes are kept. The binary MS-DOS 6 `MSDOS.SYS` is not touched. | A name is 1-8 letters, digits, `_` or `-`, not `MENU` or `COMMON`. Batch labels count only 8 characters, so the first 8 must differ from the other items'. An item whose block or label is missing shows `none` or `no label` in red: a missing label stops `GOTO %CONFIG%`. F1 shows all the keys. # Saving and backups Nothing is written until you save. F4 shows the changes so far, and F2 first shows the same review: removed lines in red, added lines in green, with 3 unchanged lines around them. F2 in the review saves: 1. A new backup set goes to `BACKUP\NNN\` next to `BMAGIC.EXE`: a byte-for-byte copy of each boot file and a `SET.INI` with the date, time, drive and a note. If the backup cannot be made, nothing is saved. 2. Each changed file is written as `X.$$$`; the old file is renamed to `X.BM$`, the new one takes its name, then `X.BM$` is deleted. If a step fails, the old file is put back. Line ends and the EOF byte stay as they were. 3. Files that had the read-only, hidden or system attribute get it back. F9 lists the backups. Enter compares one with the files on the disk in the same diff view, Ins makes a backup now, Del deletes one, and R restores one — after first backing up the files it replaces. # Building and tests The build needs [Open Watcom v2](https://github.com/open-watcom/open-watcom-v2) (in `~/.local/opt/watcom`, or `WATCOM=`), the same toolchain as the other DOS programs: ```sh SOURCE/build.sh # ../BMAGIC.EXE SOURCE/build.sh test # the test version (keys from TESTKEYS.TXT) SOURCE/test/unit/run.sh # unit tests on the host, layer check first python3 SOURCE/test/run.py # screen tests in DOSBox, on sample boot drives ``` The layers follow the [DOSLIB](https://wiki.teletypegames.org/dos/doslib) rules: `model` (the menu map, the editor, the diff, no I/O), `repository` (the boot files and the backup sets), `service`, `controller`, `view`, `platform` (the boot drive, attributes, the clock) and `app`; DOSLIB is a git subtree in `SOURCE/lib`. Woodpecker runs the style check, the layer check and the unit tests, then the build and the DOSBox tests on every push. A raised `version` in `metadata.json` (with `Version` in `SOURCE/app/version.h` raised to match), pushed to master, gets its `vX.Y.Z` tag from the pipeline, and that tag publishes a Gitea release and publishes the release to the catalog, which puts `BMAGIC` into the DOSINST store. Every step is a command of the [dos-tools](https://wiki.teletypegames.org/platforms/dos) builder image (`git.teletypegames.org/build/dos-builder`), which has the toolchain preinstalled; the repo holds only the `platform: dos` marker and its `metadata.json`, whose `dos` block says what a release holds. The screen tests run four cases at a time (`JOBS`, each in its own folder). The Gitea release is made by the [WarpEngine](https://wiki.teletypegames.org/engines/warp-engine)'s shared release step from the files `dos-pack` lists. There is no store step: the DOSINST store is the engine's DOS shelf, which it rebuilds from the catalog on every publish, so the pipeline needs no deploy key. # Limitations - At most 9 menu items, as DOS shows them. Further `MENUITEM` lines and `SUBMENU` lines are kept but not shown; the file editor (F8) reaches them. - Only the `GOTO %CONFIG%` style of `AUTOEXEC.BAT` is mapped. `IF "%CONFIG%"=="GAMES" ...` lines are kept, but a rename does not change them. - A file of at most 16000 bytes and 500 lines. - The diff looks at most 50 lines ahead for where the files agree again; larger moves show as removed and added lines. 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