http://dosbox.cvs.sourceforge.net/dosbox/dosb … DME?view=markup

The readme doesn't answer this question (comments in the configuration file do).

You need to set two things in the configuration file: windowresolution and output. Windowresolution sets the window size (e.g. 800x600). Output needs to be something else than "surface" (the others support arbitrary scaling).

If you absolutely need output=surface, you can use one of the built-in scalers to control the window size, but the options are either 2x or 3x (append "forced" if you want them to apply to text modes and high-resolution games).

Remember to set aspect=true if you want correct-looking aspect ratio.

I was able to create a file dosbox.conf according the guidelines received. However I'm not sure to understand correctly the purpose of line output=surface

As I understand , this line must be modified to something else.
What should I type to replace the word "surface" ?

And what is the specific task of line
output=blablabla ?

As for the other guidelines there was no problem.
(The config wiki helps a lot as well)

Thanks again.

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EDIT : The configuration file is being accessed correctly ; the section [autoexec] being executed when launching DosBox in Ubuntu.

But the window size is still about 1/4th of my 17" screen.
I want to scale it about 2/3 th.

I join the configuration file in attachment. What is to to change ?
Thanks

As I understand , this line must be modified to something else.
What should I type to replace the word "surface" ?

Look at the configuration file:

1# This is the configurationfile for DOSBox 0.72.
2# Lines starting with a # are commentlines.
3# They are used to (briefly) document the effect of each option.
4...
5# output -- What to use for output: surface,overlay,opengl,openglnb.

Use output=overlay, output=opengl or output=openglnb

And what is the specific task of line
output=blablabla ?

It selects the video "driver". Others except surface support arbitrary scaling.

Ok, ripa it works ok with line for the "driver" overlay
output=overlay

The DosBox window size shows bigger now.
Now I know what to change to adjust it to a appropriate size for this application.

I havn't the slightest idea which driver is the most appropriate (or most usual)
to choose from those 3, but that's another question.

Thanks again for your help.
Maybe I should have sort it out myself, but I would have lost much more time on this issue.