Quartus -multiple versions on one PC

[Altera_Forum]

Are versions of Quartus installed as independent applications? I have 17.1 installed and now I need 15.x . Thanks. 

[Altera_Forum]

Yes, they are independent

[Altera_Forum]

One note about this: if you open projects by double-clicking on their .qpf files, it may not open the version of the software you want. Adjust your environment variable (I forget which one it is) to point to the one you want to use, or be sure to open projects from within Quartus.

[Altera_Forum]

--- Quote Start ---  Are versions of Quartus installed as independent applications? I have 17.1 installed and now I need 15.x . Thanks.    --- Quote End ---    Basically, yes. They would be installed in entirely different directory structures. E.G., 17.1 under C:\Altera\Quartus\17.1, and 15.0 under C:\Altera\Quartus\15.0  I then use a command script to set the appropriate environment variables to point to one or other of the directory trees. In my case I use a shell command script:  #!/bin/bash# export QUARTUS_BASE=/cygdrive/C/Altera/Quartus/15.0 export QUARTUS_ROOTDIR=${QUARTUS_BASE}/quartus if ; then export QUARTUS_BIN=${QUARTUS_BASE}/quartus/bin64 else export QUARTUS_BIN=${QUARTUS_BASE}/quartus/bin fi export QSYS_ROOTDIR=${QUARTUS_BASE}/quartus/sopc_builder/bin export SOPC_KIT_NIOS2=${QUARTUS_BASE}/nios2eds   under CYGWIN on Windows 7 64b, but there are lots of different ways to do this using windows batch command files or other programs.