Solaris 7 is notable for being the first version of Solaris 2.x ( see SunOS, Solaris and how they relate ) to be 100% source compatible with SunOS 4.x.
It includes nearly all of the old BSD interfaces and tools, including the deprecated SunOS C compiler. Unfortunately, the SunOS bundled cc was out of date when SunOS 4.x was still current, so don't get your hopes up.
At any rate, this was no small feat for Sun. Many customers had held on to ancient SPARCstation 20's to maintain their SunOS 4 apps, and few companies made the BSD to SVR4 transition as elegantly.
See http://docs.sun.com/db/doc/805-3864 , the Solaris 7 transition guide.