save function does not work

When it try to use the save function it returns this error :

>> vars = 1;
>> save('vars')
Error using save
Unable to write file vars: too many files open.

my computer starts beeping like crazy and it goes on for several mutes (with a first phase of matlab error-like beepings, then with a different beep sound). all the function and scripts work. I tried to save my files both manually, right clicking on the variables, or using the save function (see example above). However, the variables appear in my current folder, but they cannot be opened. if i try to open one of them, this is what i get:

Error using load
Unable to read file
*directory and file name*  Too many
files open.

there are no other files open (visibly at least).

i tried:

fclose('all')
ans = 0

but still i cannot use the save function.

also :

>> close all
Too many open files. Close files to prevent MATLAB instability.

Caused by:
    Message Catalog MATLAB:services was not loaded from the file.
    Please check file location, format or contents

does not close all the figures (n = 6) open.

[madhan ravi]

which save -all % what shows up? 

[Eleonora Bano]

>> which save -all

built-in (C:\Program Files\MATLAB\R2017b\toolbox\matlab\general\save)

save is a Java method % com.mathworks.services.Prefs method

C:\Program Files\MATLAB\R2017b\toolbox\matlab\codetools\+matlab\+desktop\+editor\@Document\Document.m % matlab.desktop.editor.Document method

save is a Java method % com.mathworks.mde.editor.MatlabEditor method

save is a Java method % com.mathworks.matlab.api.editor.Editor method

C:\Program Files\MATLAB\R2017b\toolbox\matlab\winfun\@COM\save.m % COM method

C:\Program Files\MATLAB\R2017b\toolbox\simulink\simulink\@slxPackager\save.p % slxPackager method

C:\Program Files\MATLAB\R2017b\toolbox\sl3d\sl3d\@vrworld\save.m % vrworld method

[Eleonora Bano]

i ended up doing this

save('vars','-v7.3')