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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What tools were used in late MS-DOS era for reverse engineering and patching binary executables?

In the late MS-DOS era, what were the state of the art software tools for reverse engineering and patching binaries, i.e. .exe and .com files? A simple list of the tools that were "state of the art", ...
8 votes
4 answers
10k views

How do I create a boot menu to select between Windows and DOS?

I was not a PC user before Windows 98. But I remember one of my friends was using a boot menu in his 486 machine to select between Windows/DOS. The menu was like: 1. EMS 2. XMS 3. Windows If we ...
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33 votes
1 answer
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How does the command.com shell work with MS-DOS?

On my systems that are running MS-DOS, I change the default command.com to 4DOS for more features. How was the shell system designed and how did it with the operating system in MS-DOS that it enabled ...
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21 votes
1 answer
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How did large .COM files work?

An MS-DOS .com file is just raw code/data without header, thus no linking information, and was limited to be loaded into just one segment (64kB). That's the reason corrupted binaries would print "...
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29 votes
2 answers
5k views

How did MS-DOS assign drive letters in the case of more than two floppy disk drives?

The IBM PC BIOS had provisions for up to four floppy disk drives, by virtue of returning the number of floppy disk drives in a two-bit field plus a none/some flag (allowing for reporting values of 0, ...
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18 votes
2 answers
6k views

First commercial DOS game?

What was the first commercial game sold for use on IBM/MS/PC DOS after the IBM August 12, 1981 release.
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66 votes
3 answers
13k views

Why did DOS use dollar-terminated strings?

According to a few tutorials I am seeing, DOS used dollar-terminated strings to write to the terminal. This seems to also be documented here on INT 21H. AH = 09h - WRITE STRING TO STANDARD OUTPUT ...
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48 votes
9 answers
12k views

Why weren't bootable game disks ever common on the IBM PC?

While for other platforms of that era (primarily, Amiga), putting a game on a bootable disk was quite a normal practice, this approach never taken off on IBM PC. Why not? I do remember people having ...
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39 votes
2 answers
5k 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 ...
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30 votes
3 answers
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Why was the DOS clock device renamed from CLOCK into CLOCK$?

From the Wikipedia article on reserved device names ... and the CLOCK$ (still named CLOCK in some issues of MS-DOS 2.11) clock device were introduced with DOS 2.0, ... Why was is necessary to add a $...
28 votes
4 answers
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What's the relationship betweeen MS-DOS and XENIX?

Browsing MS-DOS sources on GitHub, I often see mentions of XENIX: DOSSYM.ASM: ; XENIX calls all return error codes through AX. If an error occurred then the ; carry bit will be set and the ...
26 votes
3 answers
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Why does DOS ask for the current date and time upon booting?

In most versions of DOS, when they are started from a medium that lacks an AUTOEXEC.BAT file, the very first thing COMMAND.COM does is ask the user to confirm the current date and time: Starting PC ...
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25 votes
12 answers
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Why did CP/M and MS-DOS use the BIOS instead of their own drivers to access hardware?

Modern versions of Windows (and other modern operating systems I suppose) have their own drivers to access hardware. But as I have read, in the old days, if CP/M or MS-DOS wanted to access hardware, ...
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15 votes
4 answers
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For fast scrolling DOS games, when was Mode13h preferred over Mode X?

Back in the DOS days of gaming (more specifically, 80286 - 80486 era), developers typically needed to choose between using the chunky and easier Mode 13h or the more complex "Mode X" that provided ...
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12 votes
3 answers
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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 ...
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11 votes
3 answers
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How can I create a pipe for stdin/stdout of command.com (or 4dos.com) in C or a batch file?

I'm working on a retro project and was trying to create a pipe of stdin/out/err in DOS, but I can't find any functions to to this. For instance the pipe() function from unistd.h isn't present in ...
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8 votes
4 answers
7k views

Set screen resolution in DOS-only PC

I replaced a failed CRT display with a LCD panel with a VGA controller board. There is no problem with the display when the PC boots up. However, if I switch the display off then I get an 'Out of ...
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6 votes
2 answers
1k views

How 3Dfx Voodoo 1 Emulator works

reading of this question brings up 3Dfx Voodoo 1 Emulator in my memories. I always wandered how did it work so good time as any to ask... My memory is hazy on the details so I might miss remember ...
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67 votes
3 answers
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What character is the MS-DOS cursor?

The cursor used on my 486 (and Pentium 3) in MS-DOS 6/7 has a thick underlined character. I cannot find that in code page 437. The underscore character is the closest to it, but is thinner. Where ...
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46 votes
2 answers
8k views

Did IBM encourage Bill Gates to retain the rights over PC-DOS?

As is well-known, Microsoft's negotiations with IBM to deliver PC-DOS 1.0 with the original IBM PC resulted in: IBM licensing the OS from Microsoft, as opposed to purchasing it outright. Microsoft ...
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34 votes
2 answers
7k views

Why does Windows 1.01 crash at the splash screen?

When Windows 1.01 is started under DOSBox, FreeDOS or one of the later versions of MS-DOS, garbage characters are printed on the screen right after displaying the Microsoft logo. Here’s an example in ...
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29 votes
3 answers
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Were 9.2 file names possible in MS-DOS?

In MS-DOS (and FAT16), you could only have 8.3 file names (like QUESTION.TXT) with only single-case letters and numbers (and a few symbols). The MS-DOS Editor also defaulted to 8.3 - typing edit ...
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28 votes
5 answers
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Why are Windows 95 installation disks not uniquely bound to a single product key?

I was installing the OEM version of Windows 95 on VirtualBox the other day for reminiscence sake, and for some reason I had two different product keys. I tested both of them to see which one mapped to ...
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27 votes
9 answers
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What other tricks were there to get more data onto floppy disks?

I remember using a utility back in MS-DOS 3.3 days, called MAXI Disk, that somehow magically managed to get 420K on a 360K 5¼″ disk. I assume it managed it by destroying some redundancy like a backup ...
26 votes
7 answers
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How did DOS games manage to have multiple background layers?

Seems like VGA only has one background layer, it appears to be a typical bitmap screen like most home computers of the 80s (Amstrad CPC, Commodore 64 etc.) where each pixel's color is stored in a ...
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24 votes
1 answer
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What is 'Adaptive Tile Refresh' in the context of Commander Keen?

The question Did John Carmack really invent "Adaptive Tile Refresh"? asks about the origins of the scrolling and drawing techniques used to allow an MS-DOS PC to provide a NES console-like ...
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24 votes
3 answers
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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 ...
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22 votes
1 answer
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When was QDOS changed to MS-DOS?

So a while back, I heard that MS-DOS was originally named QDOS (Quick and Dirty Operating System), and that it was later changed is MS-DOS (Microsoft Disk Operating System). This was probably a ...
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22 votes
6 answers
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Sound driver for DOS or Windows 3.x that used the PC speaker?

Long ago in a galaxy far far away, back in the early 90's, I worked for a crappy clone company as a phone technician. At the time, 386SX/25's were common for in-house technical support / customer ...
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21 votes
2 answers
8k views

What is the best way to obtain old versions of MS-DOS and Windows?

I'm wondering what the best way obtain old versions of Windows would be, specifically: DOS Windows 95 Windows 98/SE Windows 2000/ME Windows XP Professional Windows 7 Professional Microsoft Office for ...
21 votes
3 answers
5k views

Why are these DOS console drivers wasting precious bytes?

While doing some research on DOS device drivers, I took a peek at the console drivers DISPLAY.SYS and ANSI.SYS that are part of the DOS 6.20 installation. Both have "Microsoft" stamped on, ...
20 votes
1 answer
910 views

Logo of a bow tie guy with a spoon

I was in the Computer History Museum in Silicon Valley last week, and I saw this badge. I know I've seen that logo somewhere before, but I can't remember where! Does anyone know where it's from?
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20 votes
1 answer
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Why can MS-DOS not 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 ...
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18 votes
3 answers
2k 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?
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16 votes
4 answers
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Is there any way today to recover/dump 2M disks?

2M disks where formatted using 2MGUI to increase 3"1/2 & 5"1/4 DD/HD/ED disks' capacity. Is there any way today to recover/dump these disks to a file with modern hardware? Specially the 5"1/4 ...
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16 votes
1 answer
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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
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15 votes
3 answers
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Who decides what is the memory address that the CGA video buffer will be mapped to?

In DOS, the memory mapped IO base address for the CGA video buffer is 0xB8000. So when you write to 0xB8000, you are actually writing to a buffer in the CGA card itself and not to RAM. What I want to ...
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15 votes
5 answers
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Commodore Mouse not recognized by a Commodore PC30-III 286 machine

I have Commodore PC 30-III 286 machine with a serial port at the back labelled "mouse". If I plug my Commodore mouse 1900 serial mouse then execute mouse.com at the DOS prompt then I get the ...
14 votes
1 answer
2k views

Why the DOS extender and DPMI were unavailable to DOS programs on 286 standard mode of Windows 3.0

An old article on Windows 3.0 from PC Magazine (June 11, 1991, page 348) said that: Using standard mode, the Windows DOS extender and DOS Protected Mode Interface (DPMI) are available to Windows ...
14 votes
7 answers
6k views

Is there a reason why MS-DOS didn't use more English words for commands?

When using diskpart, I can list all the drives by typing LIST DISK or to select a specific drive I can type select disk 1. Is there a reason why MS-DOS didn't use more English words to do tasks, for ...
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14 votes
5 answers
3k views

Can I run Windows 98 and games from the same era on an AMD Duron CPU?

I have acquired an old motherboard with a socket 462 and a AMD Duron (I think its a "Spitfire" model 3). The copyright on the CPU is from 1999 and it apparently doesn't require a dedicated CPU fan as ...
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13 votes
3 answers
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What DOS games used Mode X as described by Michael Abrash?

In Michael Abrash's Graphics Programming Black Book, many chapters are dedicated to fast drawing of primitives, fills and copies using the 320x240 256-colour Mode X. What MS-DOS games used Mode X? ...
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13 votes
8 answers
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Why was the DOS kernel discarded?

I've read that the last DOS kernel based Windows was ME. Later versions use the NT kernel. Why did Microsoft rewrite the whole kernel? Why was the DOS kernel discarded?
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13 votes
7 answers
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Transfer files to DOS over serial cable from Linux?

I have a modern Linux computer and a 286 computer running DOS. I would like to transfer files from the Linux computer to the DOS computer over a null modem serial cable. I know you can use INTERLINK....
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13 votes
10 answers
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Alternatives for TurboVision on DOS

TurboVision was a library by Borland for developing TUI's (Text User Interfaces). It was included with their C++ and Pascal compilers. Were there any other TUI libraries that supported multiple ...
11 votes
1 answer
2k views

Timing interrupts on MS-DOS

On the ZX Spectrum, you get an interrupt every frame. As I recall, the operating system uses this to periodically scan the keyboard and probably other things also, but you can have your own routine ...
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11 votes
5 answers
3k views

Invert LCD screen in DOS 5.0

Would like to run "black on white" software on a DOS machine with an LCD screen, so am wondering if there are any TSR tools, or similar, for inverting the screen. I believe it is grey scale VGA, not ...
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10 votes
4 answers
2k views

How did DOS know where to load itself in upper memory?

If I remember correctly, you could ask DOS to load in upper memory by writing something like... DOS=UMB ...somewhere in the CONFIG.SYS file. But the question is, how did DOS know what portions of ...
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10 votes
1 answer
615 views

Is there any public documentation of the LapLink protocol?

Is the protocol used by the DOS Laplink software publicly documented? I seem to remember there were Linux tools that could use it. I cannot find anything useful on their website.
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2 answers
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Were any DOS games (or software) known to use VBE/AF?

Were there any MS-DOS games or graphics software that were known to take advantage of VESA BIOS Extensions/Accelerator Functions (VBE/AF)? some of the functions defined in the standard are ... Bit ...
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