If you are interested in downloading and trying out z390 portable mainframe assembler on Windows or Linux, here are a few startup suggestions:
For Windows Vista/XP/2000 download the latest Installshield version of z390 and install it with desktop icon for easy startup. Also download and install the latest version of J2SE runtime from Sun Microsystems. Both are free and download links can be found on http://z390.sourceforge.net.
For Linux follow the directions on the z390 Linux help pages here:
To run the WTO 'Hello World' demo program in the z390\demo directory, start up the z390 GUI or command line interface and enter the command "ASMLG demo\DEMO" to assmeble, link, and execute the demo.
Read the z390 User Guide which is in PDF format here: