For MATLAB 7.8 (R2009a) and later versions, you can determine this information by selecting the "Help>About MATLAB" Menu from the desktop.
The information also appears on the splash screen as MATLAB is starting.
If you are running MATLAB without the desktop interface, the information appears in the command window when MATLAB starts.
For previous product releases, you can determine if the version of MATLAB you are running is 32-bit or 64-bit by using the following function:
The following is the interpretation table to the ouptut of the above command:
OUTPUT OF COMPUTER VERSION OF MATLAB (32 bit / 64 bit)
PCWIN 32 bit MATLAB on Windows
PCWIN64 64 bit MATLAB on Windows
GLNX86 32 bit MATLAB on Linux
GLNXA64 64 bit MATLAB on Linux
You can specifically probe for the MATLAB bitness by using the following command:
This will return win64 for 64-bit MATLAB and win32 for 32-bit MATLAB.
You can also determine if you are running 32 or 64 bit MATLAB using the MEXEXT function which gives you the extension of the mex file generated by MATLAB:
OUTPUT OF MEXEXT VERSION OF MATLAB (32 bit / 64 bit)
mexw32 32 bit MATLAB on Windows
mexw64 64 bit MATLAB on Windows
mexglx 32 bit MATLAB on Linux
mexa64 64 bit MATLAB on Linux
mexmac 32 bit MATLAB on Mac
mexmaci 32 bit MATLAB on Intel-based Mac
mexmaci64 64 bit MATLAB on Intel-based Mac