# using GetChar on Matlab 6 for Windows **URL:** \ **Category:** Uncategorized\ **Created:** [April 17, 2001, 10:13pm UTC](https://psychtoolbox.discourse.group/t/using-getchar-on-matlab-6-for-windows/1303 "2001-04-17T22:13:10Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Allen\_Ingling](https://avatars.discourse-cdn.com/v4/letter/a/a183cd/32.png) [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)\ **Post date:** [April 17, 2001, 10:13pm UTC](https://psychtoolbox.discourse.group/t/using-getchar-on-matlab-6-for-windows/1303/1 "2001-04-17T22:13:10Z")
Chien-Chung Chen has reported that the psychtoolbox function "GetChar" when called from MATLAB 6.0 for Windows hangs Matlab. Here is a short explanation of that problem and how to avoid it. The default frontend for Matlab 6 on Windows is written in Java and executes in a Java Virtual Machine (JVM). The JVM does not interact well with psychtoolbox dlls (mex files) which access the windows event queue. However, you can run a Matlab 6 command window without using the java stuff. To do that, invoke Matlab with the -nojvm option For example, because I have installed the Matlab executable here: C:\matlabR12\bin\win32\matlab.exe To launch Matlab I type at the Windows command line: C:\matlabR12\bin\win32\matlab.exe -nojvm Typing that (and then hitting the enter key) to launch Matlab is inconvenient. Instead, you can modify a shortcut (a thing which Mac users would call an alias) to launch Matlab with the -nojvm option. In Windows 2000, right-click on a Matlab shortcut icon and select the properties item from the pop-up menu. Under the 'shortcut' tab of the properties window, find the field named 'target'. The content of this fields specifies the path to the matlab executable. Append ' -nojvm' to the path and click the 'ok' button to close the properties window. (Note the space before before the hyphen in ' -nojvm'.) Henceforth, when you double-click on that shortcut to launch Matlab it will launch without the Java stuff. Be careful, if you launch Matlab some other way, it will not launch with the -nojvm option. Some people launch Matlab from the Start menu. The Matlab entry in the Start menu tree is a Windows shortcut which you can modify as described above. In Windows 2000 that start menu shortcut for Matlab is in: C:\Documents and Settings\All Users\Start Menu\Programs\MATLAB Release 12 These instructions might be slightly different for other varieties of Windows. For example, in windows 98 the start menu shortcut is in: C:\Windows\Start Menu\Programs\Matlab. You can find all Matlab shortcuts by using Window's find utility from the Start menu. You can also relabel shortcuts to identify them as the -nojvm and regular variety. You can create new shortcuts by right-clicking on a shortcut or on the Matlab executable and selecting "Create Shortcut" from the pop-up menu. (Shortcuts created from other shortcuts point to original executable, not to the shortcut). GetChar will get characters if you use -nojvm, but be warned that GetChar still occasionally misses some kepresses. Allen > \>Date: Mon, 2 Apr 2001 14:28:02 -0700 (PDT) > \>From: Chien-Chung Chen \<[ppanthers@...](mailto:ppanthers@...)\> > \>Subject: PsychToolbox bug report > \>To: David Brainard \<[brainard@...](mailto:brainard@...)\> > \> > \>David, > \> > \>'getchar' is not compatible with MATLAB 6.0 (Release > \>12). It hangs MATLAB. The 'screen' seems working fine > \>so far. BTW. Is there any progress on "playsound" for > \>Windows? I wrote a small utility to work around the > \>problem, but I would be happy that it is in the > \>toolbox so that I can make sure my codes work the same > \>under Windows or Mac. > \> ---
**Author:** ![Allen\_Ingling](https://avatars.discourse-cdn.com/v4/letter/a/a183cd/32.png) [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)\ **Post date:** [April 17, 2001, 10:45pm UTC](https://psychtoolbox.discourse.group/t/using-getchar-on-matlab-6-for-windows/1303/2 "2001-04-17T22:45:56Z")
This is a follow-up to my previous message about the -nojvm fix for getchar under Matlab 6. You can't edit .m files from the Matlab environment if you run Matlab with the -nojvm option. One way around this is to run two instances of Matlab, one with and one without -nojvm. Use the -nojvm instance to invoke .m files and use the other instance to edit .m files. Allen "Allen W. Ingling" wrote: > \> Chien-Chung Chen has reported that the psychtoolbox function "GetChar" > \> when called from MATLAB 6.0 for Windows hangs Matlab. Here is a > \> short explanation of that problem and how to avoid it. > \> > \> The default frontend for Matlab 6 on Windows is written in Java and > \> executes in a Java Virtual Machine (JVM). The JVM does not interact > \> well with psychtoolbox dlls (mex files) which access the windows event > \> queue. However, you can run a Matlab 6 command window without using > \> the java stuff. To do that, invoke Matlab with the -nojvm option > \> > \> For example, because I have installed the Matlab executable here: > \> C:\matlabR12\bin\win32\matlab.exe > \> > \> To launch Matlab I type at the Windows command line: > \> C:\matlabR12\bin\win32\matlab.exe -nojvm > \> > \> Typing that (and then hitting the enter key) to launch Matlab is > \> inconvenient. Instead, you can modify a shortcut (a thing which Mac > \> users would call an alias) to launch Matlab with the -nojvm option. > \> In Windows 2000, right-click on a Matlab shortcut icon and select the > \> properties item from the pop-up menu. Under the 'shortcut' tab of the > \> properties window, find the field named 'target'. The content of this > \> fields specifies the path to the matlab executable. Append ' -nojvm' > \> to the path and click the 'ok' button to close the properties window. > \> (Note the space before before the hyphen in ' -nojvm'.) > \> > \> Henceforth, when you double-click on that shortcut to launch Matlab it > \> will launch without the Java stuff. Be careful, if you launch Matlab > \> some other way, it will not launch with the -nojvm option. > \> > \> Some people launch Matlab from the Start menu. The Matlab entry in > \> the Start menu tree is a Windows shortcut which you can modify as > \> described above. In Windows 2000 that start menu shortcut for Matlab > \> is in: > \> C:\Documents and Settings\All Users\Start Menu\Programs\MATLAB Release > \> 12 > \> > \> These instructions might be slightly different for other varieties of > \> Windows. For example, in windows 98 the start menu shortcut is in: > \> C:\Windows\Start Menu\Programs\Matlab. > \> > \> You can find all Matlab shortcuts by using Window's find utility from > \> the Start menu. You can also relabel shortcuts to identify them as > \> the -nojvm and regular variety. You can create new shortcuts by > \> right-clicking on a shortcut or on the Matlab executable and selecting > \> "Create Shortcut" from the pop-up menu. (Shortcuts created from other > \> shortcuts point to original executable, not to the shortcut). > \> > \> GetChar will get characters if you use -nojvm, but be warned that > \> GetChar still occasionally misses some kepresses. > \> > \> Allen > \> > \> \>Date: Mon, 2 Apr 2001 14:28:02 -0700 (PDT) > \> \>From: Chien-Chung Chen \<[ppanthers@...](mailto:ppanthers@...)\> > \> \>Subject: PsychToolbox bug report > \> \>To: David Brainard \<[brainard@...](mailto:brainard@...)\> > \> \> > \> \>David, > \> \> > \> \>'getchar' is not compatible with MATLAB 6.0 (Release > \> \>12). It hangs MATLAB. The 'screen' seems working fine > \> \>so far. BTW. Is there any progress on "playsound" for > \> \>Windows? I wrote a small utility to work around the > \> \>problem, but I would be happy that it is in the > \> \>toolbox so that I can make sure my codes work the same > \> \>under Windows or Mac. > \> \> > \> > \> To Post a message, send it to: [psychtoolbox@...](mailto:psychtoolbox@...) > \> > \> To Unsubscribe, send a blank message to: [psychtoolbox-unsubscribe@...](mailto:psychtoolbox-unsubscribe@...) > \> > \> psychtoolbox web site: [http://color.psych.ucsb.edu/psychtoolbox/](http://color.psych.ucsb.edu/psychtoolbox/) > \> > \> Your use of Yahoo! Groups is subject to [http://docs.yahoo.com/info/terms/](http://docs.yahoo.com/info/terms/)