DOS related FAQ - read here before posting




Posting Information for newbies:

You've got a problem with assembly programming?

There are probably many people who can help you solve it. You only have to do the following:

First of all, you should take a look at the
Flat Assembler Documentation ,

then you might wanna take a look at some examples in this subforum (there is an examples section , but doesn't have too much for DOS)

IF you already did so, THEN try using the search function of this message board,
IF you can't find the solution, do the following:

Try to categorize your problem, ask yourself the following questions:
Is your problem assembly related? IF NOT , THEN post to Heap
ELSE Does it belong to a specific operating system? IF YES, THEN post it to the appropriate subforum:

DOS (you are here), Windows, Linux, Unix, MenuetOS

ELSE Do you think your problem is due to some bug in FASM compiler core? (we hope not) IF YES, THEN post it to Compiler internals

ELSE Is the problem in the FASM IDE? IF YES, THEN post it to IDE Development - For developers and users of the Integrated Development Environments for flat assembler

ELSE You would like to give some feedback on the forums? IF YES, THEN post to Feedback

ELSE Post it to Main.

For advanced programmers there are also:
Macroinstructions - Post here your useful macroinstructions, discuss various tricks and syntax adjustments.
Compiler internals - Submit modifications to flat assembler itself.
OS Construction - Post here if you are writing your own OS kernel, boot loader, etc.

You probably could categorize your problem, now you may open a new topic named with the best description of your problem/suggestion, imagine if you saw that topic just created, what would you think if it had that name?

Other FAQ's:

• Flat Assembler Frequently Asked Questions (FAQ) Main
  
• DOS related FAQ - read here before posting <- you are here
  
• Windows Frequently Asked Questions (FAQ)
  
• Linux Frequently Asked Questions (FAQ)
  
• Unix Frequently Asked Questions (FAQ)
  
• MenuetOS Frequently Asked Questions (FAQ)
  
• Macroinstructions Frequently Asked Questions (FAQ)
  
• OS Construction Frequently Asked Questions (FAQ)
  

A. ABOUT DOS

0. Is [MS-]DOS dead ?

MS-DOS yes. DOS no.

t=2400

1. What is DOS ?

DOS in an alternative operating system (having old roots), focusing on size (<1 MiB) and older hardware compatibility, rather than support of newest hardware or maximum of features.

2. Where do I get DOS ?

* www.freedos.org FreeDOS (Well working, minor bugs only, written mostly in C, 16-bit, 1.0 released 2006-Sep, 1.1 released 2012-Jan)

* www.drdos.org Enhanced DR-DOS (do NOT visit drdos . com !!!) (16-bit)

* RxDOS (High-end GPL'ed DOS, FAT32 & LFN, some critical bugs remaining, originally done with MASM 5.1, port it to FASM ? NASM port in progress but not yet out, ask cm ...)

* http://freedos-32.sourceforge.net/ (32-bit, DPMI compatible, dead ?)

* http://dex-os.com/ (formerly dex4u . com ) DexOS (32-bit DOS-like OS, originally not compatible with 16-bit RM and DPMI apps, now goes DPMI?)

* http://bos.asmhackers.net/ BOS (Similar approach as DexOS, pre-alpha, toy)

* Datalight ROM DOS (reportedly "free" for personal usage, but need to "register")

* Dex4u's MiniDOS (written in FASM, nice source, but very limited in functionality, not really usable: no file I/O, floppy only, see http://board.flatassembler.net/topic.php?t=5275 )

3. What documentation on DOS or DOS programming is available ?

Some documentation exists, the problem is that much of it is obsolete or no longer easy to find.

"DOSREF" manual

t=6950 (incomplete, chapters 1...9 only, also from 1994 - not very up-to-date)

Book: "Dissecting DOS: A Code-Level Look at the DOS Operating System" by Michael Podanoffsky (Paperback - Dec 10, 1994)

"Ralf Brown's Interrupt List" (last updated in year 2000)

http://www.ctyme.com/intr/cat.htm
http://www.ctyme.com/intr/int.htm
Download HTTP : http://www.cs.cmu.edu/~ralf/files.html
Download FTP : ftp://ftp.cs.cmu.edu/afs%2Fcs.cmu.edu%2Fuser%2Fralf%2Fpub/interrupt-list/

"Forever Young Software" by Benjamin David Lunt

fysnet.net has also DOS stuff (rather old, and not FASM specific)

B. DOS AND FASM

0. Is FASM good for DOS development ?

YES.

1. What do I need ?

* DOS (see above)

* FASM DOS package (Un-ZIP it)

* Optionally an editor

* FASMD (the IDE - editor with built-in compiler) requires a DPMI host, use HDPMI32 (better, get HXRT.ZIP from http://www.japheth.de/Download/hxrt.ZIP https://sourceforge.net/projects/hx-dos/files/2.17/HXRT217.zip/download , type HDPMI32 -r ) or CWSDPMI (works also)

* No "Windows", no "Linker" etc.

2. FASM doesn't work in DOS !!!

It is supposed to and does.

1. Check your FASM version. In FASM's history many versions were released and while most of them do work well, there are a few that don't, the last known one was 1.67.25 - just download a better one.

2. FASMD ( compiler + editor IDE in one ) requires a DPMI host.

3. FASM DOS commandline version (without IDE) can use the unreal mode (just some 1.67.3xx versions had it disabled), or DPMI. However since it tries to use the unreal mode even if there is a DPMI host present, is can happen that it gets no memory and doesn't run, so opposite of problem [2]. Solutions (pick just one of them):

- Use the IDE
- Remove the DPMI host
- Add an XMS host (AKA HIMEM / HIMEMX, load before the DPMI host), then FASM should get the memory
- Use EMM386 (JEMM386/QEMM386, load before the DPMI host), them FASM won't use the unreal mode (and will require a DPMI host)
- FASM Win32 console via HX

4. Exotic CPU ? The FASM's unreal mode (see FAQ 17 below in section "E. MISC") might not work. Solutions (pick one):

- Use the IDE
- Use EMM386 to prevent unreal mode usage
- Use FASM Win32 console via HX

5. 16-bit CPU (8086 or 80286 or similar) ? Sorry, FASM needs at least 80386 on host side (and also old versions provided as COM executables need 80386). There are some other assemblers.

t=19251 2016-Jun "Cannot run fasm on HP200LX?"

C. HOW DO I ... IN DOS ?

(issues specific to DOS, interacting with DOS kernel, file I/O)

0. How to get filename of itself / current running file AKA argv[0]

http://board.flatassembler.net/topic.php?t=9872

1. How to get rid of "Abort Retry Fail" ?

http://board.flatassembler.net/topic.php?t=9740

2. How to check total/free space on volume ?

http://board.flatassembler.net/topic.php?t=8139 "GetDiskFreeSpaceEx"

3. How to read disk directory / LFN's / ATTRIB's ?

http://board.flatassembler.net/topic.php?t=7248 (ATTRIB changer by Rugxulo) 2007-Jun

http://board.flatassembler.net/topic.php?t=7247 ("DIRBUG" SFN only DIR lister with ATTRIB support by DOS386) 2007-Jun

http://board.flatassembler.net/topic.php?t=6010 (LFN DIR lister by Rugxulo) 2006-Oct

4. How to detect DOS (16-bit) version ?

http://board.flatassembler.net/topic.php?t=6772

5. How to develop TSR's ?

http://board.flatassembler.net/topic.php?t=9736 (TSR "deBUGGER", thorough design, uninstallable) 2009-May

http://board.flatassembler.net/topic.php?t=9740 (ARF hack, "strange", see [1.] above) 2009-Apr

http://board.flatassembler.net/topic.php?t=9256 "7-ZIP encryption | password in commandline | ISR & TSR !" (7-ZIP hack, cheap, no uninstall)

http://board.flatassembler.net/topic.php?t=6745

http://board.flatassembler.net/topic.php?t=6634

http://board.flatassembler.net/topic.php?t=85 "Problems setting up a TSR program"

6. How to develop SYS drivers ?

See included DEVICE example and

http://www.bttr-software.de/products/pause/ (NASM code)

7. How to develop EXE/SYS combos ?

See FreeDOS HIMEMX ...

8. How to spawn / run other executables ?

Use http://www.delorie.com/djgpp/doc/rbinter/id/51/29.html http://www.ctyme.com/intr/rb-2939.htm INT $21 / AH=$4B (this will work with DOS .COM and all types of DOS EXE files, but not with .BAT files, make sure to have free memory before calling)

http://board.flatassembler.net/topic.php?t=15668 "Execute DOS .exe or .com program in FASM" 2013-Aug

http://board.flatassembler.net/topic.php?t=1286 "EXEC: AX=4Bh How do I use this function?" 2004-Mar

http://board.flatassembler.net/topic.php?t=290 "How to execute an external program in ASM? Help please....." 2003-Sep to 2007-May

http://board.flatassembler.net/topic.php?t=9 "The function 48h fails when I want to allocate some memory" 2003-Jun (over 10 years old !!!)

9. How run a .BAT file ?

There is not straigtforward way to tell DOS to do, and INT $21 / AH=$4B will not work. But there is a hack:

t=1544 2004-May to 2004-Jul "Executing batch files..." (has code, but you should look at %COMSPEC% variable rather than hardcode "COMMAND.COM")

10. What is the structure of DOS .COM executables ?

There is none , the file simply contains monoblock code and starts at the begin, relative address of the code starts always at $0100 in the segment. Note that after loading a DOS .COM , all memory is assigned to your program, "heap" directive can't be used for COM.

11. What is the structure of DOS .EXE executables ?

t=6735 in Main (use the MZ example having "format binary")

http://www.delorie.com/djgpp/doc/exe/

12. How to create DOS executables without "format MZ" ?

t=6735 in Main (use the MZ example having "format binary")

13. How to get .COM executables > 64 KiB ? There are some around !

They are just misnamed .EXE's . Better name your executables correctly according to used file structure. DOS doesn't care about the name, if the file has "MZ" then it's loaded as MZ EXE, otherwise as DOS .COM.

14. What is the structure of DOS extended / 32-bit executables ?

The DOS kernel itself DOESN'T DEAL with extended executables. It just loads the stub (16-bit MZ EXE), and then the stub "reopens itself" ("argv[0]") and loads the main program. The stub may depend on an external file holding the dos extender ("DOS4GW.EXE") or part of it ("CWSDPMI.EXE"). Common formats are DGJPP/COFF, LE/LX, PE, NE (16-bit), and other. If the 32-bit part is small enough, it may be included in the MZ and loaded by DOS, but DOS still doesn't process it, it considers it as just "raw data" ("PKZIP.EXE").

D. COMPILATION PROBLEMS + COMPATIBILITY

0. I have a few ASM books for DOS and none of the examples works !!!

Most likely your books use MASM syntax. See Main FAQ for more info about this problem.

1. What's wrong with "mov ax,CFFFh" ?

Like some other assemblers, FASM recognizes "CFFFh" as a label, and not as a hex number, use "0CFFFh" or "$CFFF", and see Main FAQ for more info about this problem.

2. FASM whines with "reserved word used as symbol"

Instructions like MOV AX, [CX] or JMP WORD [AX] cause this error - FASM bug ?

Your BUG. Only BX, BP, SI and DI are available for indexing in 16-bit code. FASM's report is bad, but it originates from internal design. This is not a problem of DOS, but a "problem" of 8086 design and 16-bit code. See Main FAQ for more info about this problem.

3. What's wrong with "CS:[SI]" ?

SI is valid for addressing (see above), but correct FASM syntax is [CS:SI]. See Main FAQ for more info about this problem.

E. MISC

0. Can I develop GUI apps for DOS ?

YES. Use VGA:

http://board.flatassembler.net/topic.php?t=6858 (VGA 640x480x4bpp)

http://board.flatassembler.net/topic.php?t=6839 (VGA 640x480x4bpp)

http://board.flatassembler.net/topic.php?t=2187 "Hey, i'm back, 320X200 MODE STUFF, use them with care!" by Matrix

http://board.flatassembler.net/topic.php?t=2062 "0x12 graphics" 2004-Aug (banked VESA, planed VGA)

http://board.flatassembler.net/topic.php?t=1487 (link inside broken)

or VESA:

http://board.flatassembler.net/topic.php?t=16925 "VESA beginner (maybe ASM maybe C ...)" 2014-Jul

http://board.flatassembler.net/topic.php?t=10857 "gui methods in real mode" 2009-Nov (same as t=6032 below)

http://board.flatassembler.net/topic.php?t=9738 "[BUG] Ultimate VESA & INT $15 / AH=$87 test" (LFB access using INT $15, strange way to do, but works also) 2009-Nov

http://board.flatassembler.net/topic.php?t=7208 (VESA Info utility by DJ Mauretto)

http://board.flatassembler.net/topic.php?t=6514

http://board.flatassembler.net/topic.php?t=6032 "vesa problem (background, box, write text)" 2006-Oct (banked VESA)

5 VESA threads in OS construction:

http://board.flatassembler.net/topic.php?t=8160

http://board.flatassembler.net/topic.php?t=8043

http://board.flatassembler.net/topic.php?t=8028

http://board.flatassembler.net/topic.php?t=7866

http://board.flatassembler.net/topic.php?t=3559

http://brand107.home.comcast.net/pc-gpe/ (Some info on (not only) VGA & VESA)

Download: http://board.flatassembler.net/download.php?id=3915 (46 KiB, source in "C" (but "anticryptic" syntax) + DOS executable)

Download: http://board.flatassembler.net/download.php?id=3913 (580 KiB, VESA specs)

DUGL library:

http://board.flatassembler.net/topic.php?t=7133

1. How to / What is Double/Triple/Quad buffering ?

See PCTIM003.TXT text from FAQ [5.] below, it also explains this.

2. How to use the PC speaker ?

t=15339 2013-Apr to 2013-Jun "DOS Sound Effects" phone tone

t=14049 2012-Mar "PC Speaker"

t=9635 (WAV playing hints, ISA SB + PC speaker)

t=7965 (Siren sound)

http://board.flatassembler.net/topic.php?t=2432 (in Main) "PC speaker issue + code" (has PC speaker note player by Matrix)

http://board.flatassembler.net/topic.php?t=1813 "dos beeps? How do you do dos beeps? - PC speaker issue." (2004-Jul to 2004-Oct)

3. How to access ISA "soundblaster" ?

t=9635 (WAV playing hints, mostly ISA SB)

4. How to access PCI "soundblaster" / AC97 / ICH / HDA ?

See MPXPLAY source (but it's in C) and

BTTR forum id=6510 "AC97 sound driver for DOS"

BTTR forum id=10911 "SOUND support in DOS | Piotr | HDA"

SoundCardChip and "wstunjud.zip" (3 MiO)

http://board.flatassembler.net/topic.php?t=15512 "ICH4 AC97 WAV Player for DOS?"

5. How to use timers / cause a delay ?

t=15339 2013-Apr to 2013-Jun "DOS Sound Effects" phone tone , also about delaying

http://board.flatassembler.net/topic.php?t=10908 "Good alternative for high-resolution timing?" (2009-Dec)

http://board.flatassembler.net/topic.php?t=1425 "Delay" (2004-Apr)

http://www.contactor.se/~daniel/links/Pctim003.txt (<- very good)

http://www.sat.dundee.ac.uk/~psc/pctim003.txt (<- same text, alternative location)

http://www.qzx.com/pc-gpe/pit.txt

http://www.compuphase.com/int70.txt

6. Sector access to HD

http://board.flatassembler.net/topic.php?t=6841 (In OS Construction)

http://board.flatassembler.net/topic.php?t=6689 (In Main, port ATA access, mixed with file I/O and API)

http://board.flatassembler.net/topic.php?t=4305

http://board.flatassembler.net/topic.php?t=3343

7. Sector access to HD does not work !!!

Mostprobably you are inside NTVDM, not in DOS at all

http://board.flatassembler.net/topic.php?t=5626 (in Main)

8. Can I use SATA or AHCI disks in DOS ?

Sure, BIOS usually supports them (you might also check BIOS settings for "legacy IDE vs AHCI mode" or similar) through INT $13. Also, nothings prevents from using it "the low level way" in a driver or application.

http://www.bttr-software.de/forum/board_entry.php?id=7412 AHCI thread at BTTR forum from 2009-Dec

9. Can I use USB in DOS ?

Sure, use some driver or write your own, check out "USBDOS" open source driver http://bretjohnson.us/ by Bret Johnson , nice source done with A386

10. Low level keyboard detection

http://board.flatassembler.net/topic.php?t=6614 (In OS Construction)

11. Low level mouse detection / how to write a mouse driver ?

http://board.flatassembler.net/topic.php?t=15240

http://board.flatassembler.net/topic.php?t=6720 (In OS Construction)

12. Where do I find a PORT list ?

http://bochs.sourceforge.net/techspec/PORTS.LST (BOCHS emulated ports)

http://www.cs.cmu.edu/~ralf/files.html PART D of RBIL

Note that many ports are hardware specific, for example ISA sound blaster ports are completely useless for PCI sound cards, see FAQ 3 and 4 above. OTOH for example VGA (not VESA), PC speaker and PS/2 keyboard ports are pretty generic.

13. Can I develop 32-bit apps for a 16-bit DOS ?

YES.

General use16 vs use32 problems:

http://board.flatassembler.net/topic.php?t=15656 "[16/32/64] Hello, I have a couple of newbie question"

http://board.flatassembler.net/topic.php?t=6633 ( In Windows )

http://board.flatassembler.net/topic.php?t=5145 | 32-bit commands in DOS |

http://board.flatassembler.net/topic.php?t=5157 | 32 bit instructions | No need to enable in FASM ?

Use DPMI. Check the USEDPMI example and:

http://www.ludd.ltu.se/~ams/djgpp/cvs/djgpp/src/stub/stub.asm (DJASM, not FASM)

http://board.flatassembler.net/topic.php?t=8670 HX/LOADPEX and DOS/32A usage

http://board.flatassembler.net/topic.php?t=7593 Japheth's FASMHX - built-in HDPMI32

http://board.flatassembler.net/topic.php?t=6460

http://board.flatassembler.net/topic.php?t=6384

http://board.flatassembler.net/topic.php?t=6311 | Starting devel for DOS with FASM (DPMI32) | 2006-Dec

Unreal mode (see also FAQ [17.] below)

14. How to use all my RAM in DOS?

XMS or DPMI (better). Deprecated: EMS, unreal mode.

15. What DPMI / DOS extenders should/can I use ?

- HX / HDPMI32 (see links above)

- DOS/32A (needs LE-executables, no "format LE" in FASM, but

http://board.flatassembler.net/topic.php?t=8670 ( Speeeeeed thingie ... DOS/32A and LOADPEX)

http://board.flatassembler.net/topic.php?t=7122 ( Format binary as "LE" - Hello world program )

Some more:

- D3X & WDOSX (both multi-standard: raw, COFF & LE, WDOSX also PE)

Dead link D3X : http://www.geocities.com/dborca

* http://jafile.com/uploads/dos386/d3x.zip
* D3X.ZIP (dead)

* http://jafile.com/uploads/dos386/wdosx.zi7
* WDOSX.ZI7 (dead)

t=14416 New Dos Extender D3XX (derivative of D.B.'s D3X) 2012-Jul

- Causeway (Public Domain, supports DOS-specific DLL's (probably obsoleted by HX) )

Obsolete: DOS\4GW, PMODE:Orig/W/DJ, EMX/RSX, RTM:16/32, PharaoLab, ...

Unfortunately none of existing DOS extenders or DPMI hosts is written in FASM, they all have old roots, and most of them use MASM. 2 FASM-friendly exceptions are:

Tomasz's no-longer-non-public experimental HDOS written in FASM:

http://board.flatassembler.net/topic.php?t=13794 HDOS released 2011-Dec-19

http://board.flatassembler.net/topic.php?t=7988 About HDOS Extender 2007-May-19

and

Daniel Borca's D3X extender written in NASM, see above

16. Are there / will there be 64-bit extenders ?

Probably no. Many problems, very little benefit.

http://www.codecomments.com/archive258-2004-10-288963.html (dead link)

17. Unreal / Flat real / Big real / Huge real / Irreal mode ?

The real mode brings some limitations, most notably:

1. 64 KiB limit in DS
2. 16-bit code width in CS
3. 64 KiB limit in CS

According to Intel, the only way to get around is to switch to PM. However "one" found out that when switching back to RM, the CPU will forgive "forgetting" to set the DS limit back to 64 KiB, so all 4 GiB RAM and address space (including the VESA LFB) are accessible from "real" mode. This is the "standard" unreal mode used by many games, but also HIMEM, fixing just problem (1.) . But in FASM Tomasz goes one step further and also leaves 32-bit code width enabled, thus fixing additionally the problem (2.) . This currently works on most (all ?) Intel and AMD CPU's, but is more risky and might not on other models. Fixing the problem (3.) however seems definitely impossible from RM. There are opinions around that the unreal mode is deprecated, FASM continues using it nevertheless

http://board.flatassembler.net/topic.php?t=8115 ( Problem (3.) in FASM DOS (drop unreal ?) , from 2008 January )

http://board.flatassembler.net/topic.php?t=1881 ( In DOS , about FASM's unreal mode, from 2004 Jul )

http://board.flatassembler.net/topic.php?t=135 ( In OS Construction , from 2003 )

See also the KELVAR example, and MODES.INC in FASM source.

18. Integer output / garbage ???

Unlike in QBASIC, you have to convert them yourself, FASM won't do it for you. This problem is NOT DOS-specific, please look into the Main FAQ Group "E. MATH"

19. Where to find good / up-to-date info on DexOS ?

The docs on DexOS are indeed lacking. Some info here:

http://board.flatassembler.net/topic.php?t=7191

http://board.flatassembler.net/topic.php?t=7152

http://board.flatassembler.net/topic.php?t=6328

20. BUGged BUGgy BUGging ... What debugger ? How to debug ?

Japheth's deb debuggers, FreeDOS DEBUG/DEBUGX (recently also maintained by Japheth), Insight 16-bit RM debugger, GRDB, D86 and D386 (also MMX & Co) by Eric Isaacson (shareware), DOS/32A debugger, ...

http://board.flatassembler.net/topic.php?t=13973 2012-Mar "Suggested debugger for 16 bit mode"

http://board.flatassembler.net/topic.php?t=13957 2012-Feb to 2012-Mar "Suggestion: Debugger"

http://board.flatassembler.net/topic.php?t=12591 2011-Mar to 2011-Nov "Open Watcom Debugger 1.5(an excerpt) // ??????? ?? FreeDos"

http://board.flatassembler.net/topic.php?t=9792 2009-Feb to 2010-Jul "Symbolic/debug information"

http://board.flatassembler.net/topic.php?t=6203 2006-Nov to 2007-May "new version of DEBUG.COM"

http://flatassembler.net/docs/fas.zip (4 KiB -> 20 KiB TXT, last update 2012-Mar or later)

http://eji.com/a86/#OverviewD86

http://ladsoft.tripod.com/grdb.htm

http://japheth.de/debxxf.html

21. How to save DEBUG's disassembly ? Any good DOS disassemblers ?

NDISASM (from NASM)

http://nasm.us

Lack: CMP EAX, BYTE 0x02

DISTORM (semi-official disassembler of YASM)

http://www.ragestorm.net/distorm/ (was BSD, now only GPL)

Lack: MOV GS:[EAX],0x0

See Main FAQ for more disassemblers.

22. How to link FASM code with C code for DOS ?

Depends. For 32-bit DPMI code, you need a COFF linker and have to use the COFF format. For 16-bit code, there is no way to use a linker, since FASM can't output 16-bit OMF objects.

http://board.flatassembler.net/topic.php?t=10939 "16bit .obj files?"

http://board.flatassembler.net/topic.php?t=10641 "mixing fasm and pascal"

http://board.flatassembler.net/topic.php?t=8474 "Can any1 please explain how to combine Turbo C with Fasm?"

http://board.flatassembler.net/topic.php?t=8162

t=7449

t=4652 2006-Jan "MZ OBJ"

t=1659 2004-Jun "can i make obj in fasm?????"

23. 8086 compatible code, please

http://board.flatassembler.net/topic.php?t=6921 "Macros to choose target CPU" by revolution 2007-Apr in Macroinstructions

http://board.flatassembler.net/topic.php?t=6667 "is there any directive like the [cpu 8086]?" 2007-Feb in Main

24. Multitasking

http://board.flatassembler.net/topic.php?t=13430 "Quasi-multitasking in DOS"

http://board.flatassembler.net/topic.php?t=9256 "7-ZIP encryption | password in commandline | ISR & TSR !" (7-ZIP hack, cheap, no uninstall)

t=8468 2008-Mar "Multithreading in DOS : the truth is out : - ( "

t=7105 2007-May "simple multitasking in DOS via MT.COM" Note: "(c) Shamrock Software GmbH, D-85238 Petershausen, Web: http://www.shamrock.de " (MT.COM from 1'999 has just 2'319 Byte's)

X. Starting with real mode programming

0. How to write a simple Hello world program in FASM

See examples included in FASM DOS package: COMDEMO and EXEDEMO.

How to write a Hello World! Program in FASM?

How to write a Hello World! Program in FASM?
Little problem with Hello World!
Hello World! Program not working, plz help

How to use compare, jump, add and sub instructions?

80x25 text mode routines:

Dynamic Menu Structure Demonstration in Assembly (by matrix)

textmode code snipplets for newbies

Problem with a text displaying code ...

320x200x256 color graphics video mode routines:

Simple VGA mode clearscreen? Outputting Pixels to Screen? Clearing the VGA screen with specified color?

VGA tutorial

Some Frequent Problems:

Could someone give me a basic skeleton of a FASM Program?
Writing text Prints garbage! I Need help
Problem outputting strings (exe file)
Error: extra characters on line
Where can I find tutorials about ASM for easy learning??
Pls help me to convert the following code to FASM
String handling in assembly (Dos/Windows)
I need some advice, I am writing a big DOS project ...
Is there a decent viewer for Ralph Brown's interrupt list?
Program Serial Port pins for robotic projects
How to program the COM port??
Does anyone has driver loader source code ?
How to get the current time?
How to determine amount of free conventional memory?
editor + mouse in DOS
Is FASM able to communicate with QBasic Quickly and easily?

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Last update: 2016-Jul-08 by DOS386