@acer 

OK. So cat()  and  ||  are different ...

@dharr  Thanks

@Joe Riel 

"With recent versions of Maple Standard [ ... ]"

Well, I work with Maple 7. So ...

@acer 

Yes, forwardslash works too !

A last thing : I try to put in a string the most part of the path.

 > mypath:= "C:/Users/ ... /" ;

 > save G, mypath || "foo.m" ;

but that save the file mypathfoo.m in the current directory.

An idea ?

@tomleslie 

Yes, it's a very old version ! But it worked fine with Windows seven. With Windows 10, I have only somme little  problems.
Of course, using the full pathname is the best thing to do but, as I say to acer, I was never said I have to double all the backslash. it's not so obvious ... (for me).

Thanks for your answer.

@acer 

  Yes, I try but I thought it was impossible because I never see on any help that we have to double all the backslash. 

 That's exactly what i need. Thanks a lot.

OK,  I don't know what currentdir() is for. At all !

 >   currentdir() ;

give "C:\\WINDOWS\\System32"

but "foo.m" is not there.

In fact, I find it with the File explorer.
I recall that the funtion "search" of  Windows can't find it!
I foolishly thought that it was the same thing ! 

On my computer (Windows 10), I found it in C:\ ... \AppData\Local\VirtualStore\Windows\SysWOW64
On my older computer (Windows 7) the file were in C:\ ... \AppData\Local\VirtualStore\Programfiles(x86)\Maple7

Thanks a lot for your answers.

Thanks, I try it.

 > G:=120120 ; save G, "foo.m" ;
    G:=1 ; read "foo.m" ; G ;

give correctly 
                             G := 120120
                                G := 1
                                120120

but now

> currentdir("foo.m");

give : " Error, (in currentdir) file or directory does not exist ".