Unable to determine the execution envoronment of the Intel<R> FPGA SDK for OpenCL<TM

At a command prompt, invoke the aoc --version command.

Example output:

aoc: Unable to determine the execution envoronment of the Intel<R> FPGA SDK for OpenCL<TM>

aoc: Detailed error: Internal error: Path to SOPC Builder directory us not found!

Who can tell me why?