Must copy and rename file
Solution 1:
Copy and rename in the same time (also change filename, not only path):
cp program3.cpp homework6.cpp
Rename only:
mv program3.cpp homework6.cpp
Solution 2:
If you want to have the files permanently linked use the ln command instead of cp
ln program3.cpp homework6.cpp
This puts a file descriptor (hard link) under the name homework6.cpp to the same file location as program3.cpp