ms-dos interview questions

Top 15 ms-dos interview questions

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How can I get more low memory with the following setup:

Modules using memory below 1 MB:

  Name           Total       =   Conventional   +   Upper Memory
  --------  ----------------   ----------------   ----------------
  MSDOS       14 317   (14K)     14 317   (14K)          0    (0K)
  HIMEM        1 120    (1K)      1 120    (1K)          0    (0K)
  EMM386       3 120    (3K)      3 120    (3K)          0    (0K)
  OAKCDROM    36 064   (35K)     36 064   (35K)          0    (0K)
  POWER           80    (0K)         80    (0K)          0    (0K)
  NLSFUNC      2 784    (3K)      2 784    (3K)          0    (0K)
  COMMAND      2 928    (3K)      2 928    (3K)          0    (0K)
  MSCDEX      15 712   (15K)     15 712   (15K)          0    (0K)
  SMARTDRV    30 384   (30K)     13 984   (14K)     16 400   (16K)
  KEYB         6 752    (7K)      6 752    (7K)          0    (0K)
  MOUSE       17 296   (17K)     17 296   (17K)          0    (0K)
  DISPLAY      8 336    (8K)          0    (0K)      8 336    (8K)
  SETVER         512    (1K)          0    (0K)        512    (1K)
  DOSKEY       4 144    (4K)          0    (0K)      4 144    (4K)
  POWER        4 672    (5K)          0    (0K)      4 672    (5K)
  Free       552 944  (540K)    539 088  (526K)     13 856   (14K)

Memory Summary:

  Type of Memory       Total   =    Used    +    Free
  ----------------  ----------   ----------   ----------
  Conventional         653 312      114 224      539 088
  Upper                 47 920       34 064       13 856
  Reserved                   0            0            0
  Extended (XMS)*   64 898 256    2 671 824   62 226 432
  ----------------  ----------   ----------   ----------
  Total memory      65 599 488    2 820 112   62 779 376

  Total under 1 MB     701 232      148 288      552 944

  Total Expanded (EMS)                33 947 648 (33 152K
  Free Expanded (EMS)*                33 538 048 (32 752K

  * EMM386 is using XMS memory to simulate EMS memory as needed.
    Free EMS memory may change as free XMS memory changes.

  Largest executable program size        538 976   (526K)
  Largest free upper memory block          7 488     (7K)
  MS-DOS is resident in the high memory area.

I'm running MS-DOS 6.22 on VMWare virtual hardware. This is memory state after MEMMAKER pass, so i'm looking for optimization beyond MEMMAKER.

Note: NLS drivers (DISPLAY, KEYB, NSLFUNC) are essential for me.

Thanks to @mtone for valuable reminder about MSCDEX /E which gave me 16KiB of low memory (see the diff)!

Source: (StackOverflow)

What are the replacement options for an IDE hard disk for a DOS based system?

I have got a few "embedded" systems running MSDOS 6.2 which boot from and store data to IDE hard disks. Since these drives are nearing their end of life, the question arises how we can replace them.

The requirements are:

  1. DOS must be able to install and boot from these drives.
  2. They must be able to sustain heavy (mostly) write access.
  3. If possible, they should be able to survive moderate vibrations (not too bad since the current hard disks have survived several years of that)

I considered the following options so far:

  1. other ide hard drives: Unfortunately modern IDE drives are too large so DOS cannot boot from them even if I create small partitions. Older IDE drives are just that: old, so they are probably not the most reliable ones any more.
  2. SSDs: There are a few SSDs with IDE interface available. I have not yet tried them. Does anybody have any experience with them? They look like the ideal replacement provided that DOS can boot from them and that writing speed does not deteriorate too much (the old hard disks are no race cars either).
  3. Compact Flash: There are adapters for using CF with IDE controllers and they work fine. DOS can boot from them and they have no problems at all with vibrations. What I am not sure about is their durability. DOS uses FAT so some very few sectors are written every time the medium is being written to.
  4. IDE to SATA converters: I have no idea whether they are any good. Has anybody tried them? It might be an option to use one of these to connect an SATA SSD to the system.

Are there any alternatives that I have missed? (We are working on replacing these systems, but it will still take a few years.)

Source: (StackOverflow)

Is it better to turn off computer or power continuously to keep ancient 1990 harddrive alive (MSDOS 6.22 )

I want to extend the life of this harddrive as much as possible because I found it nearly impossible to clone.

It is running MSDOS 6.22. 110mb harddrive from 1990. The computer is only utilized 1 hour a day, 5 days a week.

If I want to keep it alive as long as possible, is it better to turn this computer off everyday or keep the computer powered on 24/7?


Edit: I tried using dd_rescue and clonezilla to try to duplicate the contents of the harddrive, but no mater what I do, the harddrive never boots into msdos. I spent half a week trying to clone it.

I am not concerned about anything but the hard drive because it is irreplaceable unless I can manage to successfully clone it.

More info: The computer hardware is a modern early 2000's pentium 4 dell. Only the harddrive is ancient

Source: (StackOverflow)

best way of moving files to a DOS machine?

I've got an old DOS (read: abandonware) machine running my old DOS games (as referenced here). I'm finding that over time, my floppies are starting to die and become completely unreadable.

So recently i've been finding abandonware binaries of games i currently own and have downloaded them to my Vista box.

Vista machine has no floppy drives but has a CD/DVD-R. Vista machine has no serial or parallel ports. DOS machine has floppy drives but no CD/DVD drive. (it does have a 100mb HDD though) Amazingly, both machines have USB and ethernet. DOS machine has some ancient 3Com 10BT card.

I can't seem to figure out how to get FTP much less a TCP/IP stack up and running on the DOS machine, and no forms of USB storage have been readable on both machines.

Whats the best way to get these binaries over to the DOS machine?

(I know this is starting to sound like that age old question of how to move the fox, baby, and bag of grain across the river on a boat that only seats two)

Source: (StackOverflow)

In Windows Explorer, why can we create a folder or file with the percent (%) symbol, if the percent symbol is used for existing variables?

  1. Go to Windows Explorer, and create a folder/directory named %systemdrive%, %windir%, or any other existing variable.
  2. Open a command prompt, and go to the folder you just created.

You can't, because there are percent (%) symbols in the folder name, confusing the command prompt, because the percent symbol is used for existing variables.

Escaping the percent (%) symbol with two percent symbols (%%) does not work, so DavidPostill's answer is wrong:

Command prompt window, with a bit of the Explorer desktop showing So, in Windows Explorer, why can we create a folder or file with the percent (%) symbol, if the percent symbol is used for existing variables?

Source: (StackOverflow)

Is it possible to run an old 16-bit DOS application under Windows 7 64-bit? [duplicate]

Possible Duplicate:
Why 64 bit OS can't run a 16 bit application?
How do I get 16-bit programs to work on a 64-bit Windows?

Here at work my new development machine is Windows 7 64-bit (so I can use extra memory and run VMs). However I have a dilemma: it appears that 16-bit DOS programs do not run under Windows 7 64-bit.

I have an old legacy program written in Clipper that I need to run periodically.

I cannot access the compatibility setting as Windows 7 just greys them out.

Source: (StackOverflow)

Transferring "large" file off of MS-DOS 5.0 Machine (without removing HDD)

As part of some sort of legal record-keeping thing, my father's business lawyers has requested a copy of the database of customers from a work computer. The core issue is that this work computer is a circa 1988 AOpen...thing, running what looks to be a modified version of DOS 5.0.

I'm very weak with actual MS-DOS, and older hardware in general, but after some fuddling around I finally found the file that the lawyer needed. The issue comes that the customer "database" (read: space delimited text file) is ~3MB big. This is too big for one floppy, and the data is in one single file, which, to my very limited knowledge of actual DOS, would preclude me splitting it with the built-in programs on the computer.

Checking the back of the computer, I noted 1 built-in serial port, a parallel port in an expansion slot, and somewhat inexplicably, a NIC with a jack in it too big to be RJ-11. I didn't test if it was actually a RJ-45 as I didn't have an ethernet cable handy at the time. However, the two program files that I would have used (according to my research) to use the serial are nowhere to be found on the computer. Furthermore, I haven't the slightest idea what I would do to leverage the NIC.

Furthermore complicating issues, just pulling the HDD has to be relegated to a last resort, as the computer (which is older than I am) is used for daily business operations and would have to be taken offline for around 1 day due to the distance between the computer and me, which the "client" does not particularly want.

So the crux of my question is, with my almost none existent skill in DOS (I accidentally corrupted one of the "databases", and would have been in bad shape if I didn't make a backup beforehand), is there a simple way I can leverage the above-mentioned assets (or something else I don't know about DOS) to get this 3 meg file off of the computer without pulling the HDD?

Source: (StackOverflow)

What is the difference between CMD and Command prompt in windows?

Until now, I never thought (and never observed) that cmd and command are two different things. Well, are they?

Take a look at this pic:

enter image description here

Actually, I usually open cmd from the Run dialog whenever I want to command-line (for Git/ VIM). So, I customized the display position, font, color, etc. Today, I, for a change, typed command in Run instead of cmd and found that there is something new on my window. It has "DOS" in its window.

So, obviously there should be difference between cmd and command. I would like to know

  1. The difference between them.
  2. Why Microsoft separated them (Unix & Linux has only one shell by default, Bash).

Source: (StackOverflow)

Using Win32 in DOS

Is there a way that I can start the Win32 environment or run Win32 programs from DOS without starting the Windows GUI?

I'm using a Windows 98 PC that is booted into DOS mode from a floppy disk.


I want to run command line programs. Some of these are Digital Mars C and .NET Framework.

Source: (StackOverflow)

Are the Command Prompt and MS-DOS the same thing?

I argued with my friend that the Command Prompt is just a GUI version of MS-DOS which works in the Windows forms environment. He totally disagrees with me.

Who is right?

Source: (StackOverflow)

How to install MSDOS from floppy to harddrive?

I have a bootable MSDos system. I would like to install it on the current PC so that I can boot from HDD instead of Floppy. How can I do that?

I am doing this in virtualbox, but a general solution would be nice.

Source: (StackOverflow)

Do you have to install DOS 6.22 before installing Windows 3.0?

I've been tasked with creating a VM with Windows 3.0 and Office 3.0 on it. I have the install disks for Windows and Office but not for DOS. Do I need to have DOS installed first to install Windows 3.1?

Source: (StackOverflow)

Is there a way to append files efficiently using the DOS copy command?

Using the DOS copy command syntax to concatenate files:

copy file1.txt+file2.txt all.txt

I know I can do this...

copy file1.txt+file2.txt file1.txt

Is this efficient? Is it doing what I'm expecting? It works, but I want to know is it actually appending to file1.txt or is it copying file1.txt (bad), concatenating file2 and then renaming to file1.txt (which is not efficient)?

Source: (StackOverflow)

MS-DOS command to delete all files except one

Is there an MS-DOS command that allows me to delete all files except one?

Consider as an example the following files:


Is there a command to delete all files except a.c?

Source: (StackOverflow)

Fullscreen digital clock for DOS 6.22?

I came across a Dolch L-Pac 586 a few months ago. My boss was going to throw it out, but I managed to convince him to let me give it a home. Since then, I've been wracking my brains, trying to think of a clever use for it. I have been thinking that it would be really awesome to get some sort of fullscreen digital clock program and just use it for a timekeeping device / conversational piece. (It's got an extremely sharp 9" screen - absolutely zero LCD rot.)

Anybody have any idea what I could use?

Source: (StackOverflow)