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Questions tagged [ms-dos]

MS-DOS, the Microsoft Disk Operating System, its OEM-branded versions, and x86 DOS clones in general.

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4 votes
3 answers
3k views

Why is the "jmp" instruction not working if I put data before it?

I have written the following program in debug.exe: 1165:0100 mov ah, 09 1165:0102 mov dx, 107 1165:0105 int 21 1165:0107 db 'Hello World', 0A, 0D, '$' 1165:0115 jmp 1165:0100 However, when I ...
0 votes
1 answer
197 views

Installing MS DOS 6.22 under VMWARE

I want to install MS DOS 6.22 as a guest os under VMWARE. I have a bootable msdos.iso file. When I try to create a new guest using this image file VMWARE successfully boots from this file and gives an ...
17 votes
1 answer
7k views

How to write directly to video memory using "debug.exe" in MS-DOS?

The base address for the video memory in MS-DOS is 0xB8000. I am trying to write to this address using debug.exe, but I am getting an error: 1165:0103 mov [b8000],ax ^ Error
21 votes
7 answers
8k views

Are there any good, non-abandoned PC emulators?

Mission: I'm trying to simulate a classic ~286/386/486/Pentium inside my modern PC (running Windows 10) in the most authentic way possible. Just a quick note to say that I (Sarah Walker) have decided ...
39 votes
11 answers
9k views

Is there a reason to prefer earlier versions of MS-DOS over later?

I understand MS-DOS to be backwards-compatible, so is there a reason to run a version earlier than the last (6.22) on an old computer? The only reason I can think of would be for period-accuracy, but ...
13 votes
5 answers
3k views

What are the minimum system requirements to run GW-BASIC?

In DOSBox 0.74, I can run GWBASIC.EXE without any problem (DOSBox reports 632 KB of free conventional memory). It is GW-BASIC's version 3.10 dated 01-07-1989 with filesize 72576 bytes. On screen it ...
13 votes
13 answers
1k views

Towards people who were there, what programs did you use to develop applications for the IBM 5150?

I want to get into programming on old MS-DOS systems, before then going to older DOSs like CP/M. However, while programming for MS-DOS I'd like to also use era-appropriate software, both for the ...
22 votes
3 answers
3k views

Is there a technical reason why Datel Action Replay on PC required a card?

In the mid-90s, there was an ISA expansion card called “Datel Action Replay” that could be inserted into almost any PC-compatible machine (e.g. 80286). By pressing a button on a device (plugged into ...
10 votes
1 answer
3k views

Is there any DOS game before Quake era (1996) that makes heavy use of the FPU?

Quake was one of the earliest DOS games to show most gamers the importance of having a fast FPU to play with. Were there any other games (probably 3D) before Quake that started using the FPU? For ...
0 votes
1 answer
400 views

What does this triangle rasterization code do? What does it use a “depth cueing table” for? [closed]

Who can explain to me what is the depthq_table, how is it built, how the function works gtmap_persp32_fp, how arranged perspective correction every 32 pixels in this function? That is, as I understand ...
30 votes
4 answers
6k views

Most modern C compilers targeting DOS 8086, running on DOS 8086 (16-bit)

I'm looking for the most recent versions of modern C compilers which were/are targeting DOS 8086, also running on DOS 8086 (16-bit). I'm mostly interested in production-ready C compilers, rather than ...
3 votes
2 answers
2k views

Educational DOS game involving teddy bears

I remember when I was very young (mid-to-late 90s) playing a probably educational DOS game that was like a whole bunch of minigames. At least one of the minigames (perhaps all of them) was teddy-bear-...
20 votes
1 answer
2k views

Why is MS-DOS not able to read partitions starting at logical sector 0?

When creating a FAT file system, mtools and newer versions of mkfs.fat write a stub MBR partition table to the boot sector. This makes the file system accessible when written directly to media that ...
5 votes
3 answers
577 views

Why is memory below the stack pointer constantly being overwritten under a debug session?

When I run a debug session using FreeDOS and DEBUG.EXE, I get a session like the following. I've added a description of what I saw as annotation on the image. Each step, I've printed out the stack ...
28 votes
3 answers
10k views

Was the MS-DOS window in Windows 95 an emulator like current DOSBox?

Windows 1.x, 2.x and 3.x required a DOS to be loaded before running them. Later Windows 9.x and ME had similar (?) way of working, but DOS was included with them, 32-bit multitasking and other stuff ...
2 votes
0 answers
151 views

Using 386SWAT to trace a program through a transition from real mode into protected mode

The 386SWAT debugger seems to be able to continue tracing a real-mode (not V86) program that goes into protected mode, but I don't quite understand how to configure 386SWAT, and I can't find any ...
24 votes
3 answers
7k views

Was OS/2 a viable alternative for daily DOS and Windows tasks?

After playing a bit with the OS, a question sparked my interest: Could it entirely replace DOS and Windows ? Let's restrict the scope of this question a bit since it's fairly broad, Was it ...
36 votes
4 answers
8k views

Did any MS-DOS program ever use the System Request interrupt?

As I remember, the SysRq key generated a special, unique interrupt (not an ordinary keyboard interrupt). It was supposed to let the user interrupt any process in a multitasking situation and return ...
7 votes
1 answer
522 views

Why is the Compaq FWS2ASPI.SYS driver not recognized as an ASPI driver?

I have a Compaq ProSignia server with an onboard NCR53c710 EISA SCSI controller. Compaq supplies a driver for it (the latest version is contained in the SoftPaq 10751 (SP10751.EXE), called FWS2ASPI....
19 votes
6 answers
4k views

What are my options for multitasking in MS-DOS 5.0 on an 80186 with EMS?

I've got an HP 200LX, which runs DOS 5.0 from ROM, and I'm using EMM200 to provide some EMS from the C: RAM disk (it uses the memory controller to directly map the "disk" blocks into memory, ...
15 votes
4 answers
3k views

Can DOS make use of more than 640 KB of conventional memory on 80186?

Can I have more than 640 KB conventional RAM under some DOS? I'm looking at an 80186 PC that has RAM at address A0000. Video RAM starts at B0000 as expected for a Hercules; A0000 is just more main ...
15 votes
5 answers
2k views

DOS: How do I type an ANSI escape sequence?

I'm currently trying to experiment with ANSI escape sequences on various terminals/terminal emulators, so I'd like to know if there's an expedient way of typing these sequences on a DOS command prompt,...
44 votes
2 answers
7k views

How did Windows ME "cripple" DOS?

Windows ME includes the ability to create a bootable DOS floppy. This floppy contains versions of COMMAND.COM and IO.SYS that are "crippled" to remove real mode. This is done with only one changed ...
12 votes
3 answers
3k views

Disassembling Windows IO.SYS

Under the question How did Windows ME "cripple" DOS?, Ross Ridge's answer showed a section of his disassembly. I would like to know, a) what disassembler was used and b) what adjustment or ...
-4 votes
1 answer
284 views

Does DOS run Crysis? [closed]

There certainly exist machines that can run both DOS and Crysis, but both at the same time? I had something like the HX DOS extender in mind and mesa3d can be compiled for DOS and Windows. There seem ...
20 votes
6 answers
13k views

Why didn't PC games eschew MS-DOS and deal with BIOS directly?

Given the memory referencing limits of MS-DOS for compatibility purposes, why didn't games produced for the 286+ processors eschew MS-DOS and talk directly with the BIOS or IO hardware, instead of all ...
19 votes
3 answers
3k views

How did DoubleDOS work?

Back in the MS-DOS days, there was a program DoubleDOS that you could run that would split your machine in half and multitask two separate DOS programs. While it didn't particularly work well for ...
44 votes
9 answers
12k views

Is DOS being shipped with or as an installed OS?

Given the very small size of DOS, it would seem it might still be ideal for some applications such as handheld games. Is any system manufacturer still shipping DOS with their machine? If no one is ...
11 votes
5 answers
6k views

How did 16-bit MS-DOS programs use a large (> 64KB) stack?

The "large" memory model of x86 allowed a program to have multiple code segments and multiple data segment, using far calls to jump across code segments, and far pointers to access data from ...
21 votes
5 answers
4k views

How can I reverse-engineer the game Wizardry (1981) for PC, based on UCSD Pascal?

I am looking at the files included with the 1981 game Wizardry. The particular version I have is from a 1998 re-release, but I do not know if the binary is still the original 1981 release. My ...
35 votes
3 answers
5k views

Why did DOS-based Windows require HIMEM.SYS to boot?

My understanding is that all versions of Microsoft Windows that ran on top of DOS — that is, the lineage from Windows 1.0 up to Windows ME, even though the reliance on DOS diminished over time — ...
24 votes
7 answers
6k views

Did MS-DOS have any support for multithreading?

Common wisdom seems to be that MS-DOS was an exclusively single-threaded OS. Of course, implementing a scheduler would be possible, but the OS itself did not provide any facilities for multithreading, ...
23 votes
9 answers
8k views

Why did "protected-mode MS-DOS" never happen?

Software written for MS-DOS used DOS extenders as early as on PC/AT (DOS/16M), and starting from i386-based systems, DOS extenders became really widespread. I'd think it was pretty obvious at the time ...
21 votes
6 answers
7k views

How can I emulate MS-DOS on OS X?

I am looking for a emulator for MS-DOS for OS X to run old games on. Are there any free emulators for MS-DOS that run on an Apple machine with OS X?
23 votes
3 answers
4k views

What were the actual memory model definitions in MS-DOS?

I've heard the phrase "memory model" used in relation to MS-DOS programming (and early Windows), with terms such as "small" and "compact". But what were the actual ...
22 votes
3 answers
3k views

Why did MS-DOS choose the percent symbol to designate variables?

I couldn't find anything but is there any reason for choosing % over $ like in *nix shells?
3 votes
2 answers
486 views

Why does my MZ executable's BSS inflate by ~1,5KB after linking fopen() with MSC?

For a game reversing project, I am trying to undo linking with the C library performed by the MSC 5.1 C compiler+linker. To that end, I have created a simple executable that does nothing except ...
32 votes
1 answer
3k views

Did DOS zero out the BSS area when it loaded a program?

As an example, say we have a DOS MZ EXE file that's around 20 KiB in size. The EXE header contains the value 0x1400 at offset 0x0A indicating that the program is requesting 5,120 paragraphs (or 80 KiB)...
62 votes
7 answers
11k views

Why did some old MS-DOS games lack the ability to exit them?

While playing around in DOSBox-X, I'm reminded of some DOS games which appear to entirely lack the ability to exit/quit/close them. One prime example of that is "Paratrooper" from 1982. I've ...
37 votes
6 answers
13k views

Is there a simple way to display ANSI art and animation files in a modern terminal window?

ANSI art and animations were prevalent on BBS systems in the late 80s and early 90s, and the ANSI art scene continues to thrive today. There are thousands of ANSI art files, with usual extension .ans, ...
26 votes
3 answers
14k views

Why was "C:" chosen for the first hard drive partition?

I was reading this answer, as the question came to my mind: why does C: indicate the first hard drive partition? The usage dates back to CP/M (as noted in a comment), was embraced by MS-DOS, and ...
7 votes
2 answers
3k views

How does 2M for DOS (2 MB formatted floppy disks) achieve what it does?

This is the program and technique in question: https://dbpedia.org/page/2M_(DOS) Also described here: https://en.wikipedia.org/wiki/2M_(DOS) And here is the unintelligible explanation from the website:...
20 votes
2 answers
3k views

In 16-bit MS-DOS, how do I get a file handle to the currently running .exe?

The context is that I have additional data in the .exe file and wish to access it. I know this is possible, as plenty of programs would store extra data after the loadable part of an MZ .exe — most 32-...
10 votes
2 answers
2k views

How to use all memory on an IBM PC with 8086

I'm developing software for the IBM PC with an 8086 processor. I want my program to use all available memory. I know that I can use DOS int 21h function AH=48h to allocate all available conventional ...
10 votes
3 answers
959 views

How can I make the Microsoft C compiler for DOS emit a loop with an intermediate jump to continue?

I am trying to recreate the exact C source code from some 16bit DOS 8086 assembly generated by the MS C 5.0 compiler. After making some progress, I've hit a wall with the following code (annotated in ...
8 votes
1 answer
672 views

How to make Microsoft C for MS-DOS emit an immediate-target far call into the data segment?

I am trying to recreate the C source code from some 16bit DOS 8086 assembly generated by the MS C 5.0 compiler. I've hit a wall with this far call instruction. 0000008D 9A2F0CB506 call 0x6b5:...
2 votes
3 answers
745 views

What binary format did QuickBasic use for BAS files?

I found some very old floppy disks. I sent them to a company to restore the files and they were still retrievable! Next to old games and simcity save games I found some .BAS files. Some of the names I ...
6 votes
1 answer
238 views

How to run MOUSSUBS.BAS in QuickBasic? Looking for MIXED.QLB and MOUSE.ASM?

I retrieved some 30 year old basic files from old floppy disks. Now I am trying to run some games I made back then. Some of them are actually dependent on this file called MOUSSUBS.BAS. That file ...
20 votes
2 answers
2k views

Which is the first version of DOS to support more than one reserved sector in a FAT file system?

I'm trying to fix a problem when trying to use DOS stuff on SSDs. The problem is sector alignment in an SSD is completely different from what DOS expects, and writes to FAT do funny things when the ...
4 votes
1 answer
209 views

Tandy 1000 TDYSPKR utility

I've seen reference to a TDYSPKR (.EXE or .COM?) tool that sets audio output options on the early Tandy 1000 series of computers (1000, 1000A, 1000SX, 1000TX, maybe others). Apparently it can toggle ...

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