That's an '86 CRX DX.

And yes, the CRX's and Del Sol's are Civic platform cars, and are nearly identical from the A-pillar forward [edit: compared to their similar generation Civic counterparts]. Aft of the A-pillar they are obviously quite differently designed unibodies.

As for the Del Sol, in Japan they were known as Civic CRX Del Sol's. In Europe they are sometimes called 3rd Gen CRXs. The reason they were never called CRXs in the states is due to the findings of a research panel for Honda that found that the American buying public tended not to buy cars that had long names, so they dropped Civic and CRX off the name and just sold them as Honda Del Sols.