Using DOSBox with CCS Emulators

Some of the Computer Conservation Society’s computer emulators are MS-DOS or PC-DOS programs written as long ago as the 1980s and 1990s. They may not run (without assistance) on current versions of Microsoft Windows. There are two problems:

  • 16-bit programs are incompatible with 64-bit versions of Windows. (They may still run on 32-bit versions of Windows.)
  • Some programs require “fullscreen mode” which is no longer supported.

You may get an error messages like one of these:

(Attempting to run in cmd.exe on 64-bit Windows 10)

(Attempting to run in cmd.exe on 32-bit Windows 7)

(Attempting to run as a Windows executable file in 64-bit Windows 10)

(See Microsoft knowledgebase article: )

There is an easy way round these problems: DOSBox is a freeware DOS emulator written for running classic computer games. It works equally well for computer emulators. It appears as a window containing a DOS command line interpreter. DOSBox is well documented on the web. There are examples of its use on YouTube and a full User Manual included in the download.

Installing DOSBox for running CCS emulators

  1. Create a folder to accommodate the troublesome emulator(s):
    - e.g. A folder called “DOSems” on the desktop. (Folder names are not significant, so long as they are used consistently, so you can choose a different one if you wish.)

  2. Download and install DOSBox from
    - Click on “Downloads” (just under the banner heading).
    - In the “DOSBox (specific versions)” panel, click on “Windows” to download the installer file “DOSBox0.74-win32-installer.exe”. Save it to your desktop or Downloads folder. (0.74 is the DOSBox version number at time of writing.)
    - Double-click the downloaded installer file and follow the onscreen instructions to install DOSBox.

  3. Mount the folder created in step 1 as a virtual hard drive in DOSBox:
    - From the Windows Start button, find “DOSBox-0.74” in “All Apps” (or “All Programs”), click to expand it and select “DOSBox 0.74 Options” (or “Options” and then “DOSBox 0.74 Options”).

    The configuration file opens in Notepad.
    - Scroll down to the very end of the file where you’ll find:

    # Lines in this section will be run at startup.
    # You can put your MOUNT lines here.

    - Add three more lines:

    MOUNT C C:\Users\Steve\Desktop\DOSems

    Modify this example so that the first line mounts your new folder on what DOSBox regards as its “C: drive”. (If you aren't sure of the path name, right-click the folder and select ‘Properties’ so that the ‘Location’ is displayed.)

    The second line configures DOSBox for a UK keyboard. For other countries see (Note that KEYB is in upper case.)
    The third line changes directory from the default Z:\> to C:\>.

    - Finally, save the configuration file (File menu > Save). DOSBox is now ready to use.

  • When running a computer emulator in DOSBox, clicking within the DOSBox window is usually sufficient to associate the Windows cursor but, when this happens for emulators with a graphical user interface, the cursor can become confined to the window. Release the cursor, when you wish to exit, by typing Ctrl+F10. (i.e. Press F10 while pressing Ctrl.) See, also, the note in the PegEm2 example below.
  • DOSBox runs in a window with a default resolution of 640x480. This can be changed:
    To run “fullscreen”, press Alt+Enter on the PC keyboard at runtime.
    Press Alt+Enter, again, to return to a window.
    If you prefer a different default window resolution, edit the configuration file:
    - Open the configuration file as in step 3 of “Installing DOSBox... ” above.
    Find “windowresolution=original” and try changing it. For example,
    windowresolution=1280x960” will double the window size. (You will need to alter “output=surface” to one of the other values listed in the comment just above it. e.g. “output=opengl”)
    - Save the edited file (File menu > Save)
  • The emulated processor’s speed can be changed, too:
    - Ctrl+F11 decreases, Ctrl+F12 increases the speed in steps. (Press more than once as required at runtime). Or the default value can be changed by editing the configuration file. (Find the “[cpu]” section.)
  • For a list of the most useful DOS commands, type “help” at the command prompt (without the quotes). “help /all” gives a complete list.

Example: Running the Ferranti Pegasus emulator, PegEm2, in DOSBox

  1. Download “” from the CCS website. Extract all files into a new folder, called “Pegasus”, say.
  2. Copy or move the Pegasus folder into your DOSems folder.
  3. Load DOSBox by double-clicking the desktop shortcut (or find it via the Windows Start button).
  4. Within the DOSBox window, start the Pegasus emulator:
    C:\> cd Pegasus
    C:\PEGASUS> PegEm2

    The emulator loads and is ready to use.

    Note: PegEm2’s interactive graphical user interface (GUI) opens after typing ‘S’ for ‘Simulate’ (as shown on the displayed menu). The GUI has an illustrated hand, the forefinger of which is a graphical cursor for operating the dials and handswitches. The Windows cursor does not automatically associate with the graphical cursor. To make that connection, press Ctrl+F10. This will lock the PC’s cursor to the tip of the forefinger (and will confine it to the DOSBox window). To release the Windows cursor afterwards, press Ctrl+F10 again.