Certain Solaris 7 system packages provide both 32-bit and 64-bit versions. For example:
The SUNWcsl package contains core 32-bit Solaris shared libraries.
The SUNWcslx package contains the Solaris 64-bit versions of the core shared libraries.
You can add 64-bit application tools (64-bit shared libraries) to 32-bit platforms if you want to develop 64-bit applications on a 32-bit system.