An apparatus which is an integral hardware consisting of an annular downer reactor and a concentric upflow riser regenerator for catalytic cracking of hydrocarbon feed to is disclosed. The annular downer reactor terminates in annular stripper which is also concentric with the regenerator. The regenerator, reactor and stripper are in fluid connection with each other. The apparatus is highly compact and provides efficient contact between circulating catalyst and hydrocarbon feed. The proposed hardware includes a novel radial distributor for providing improved control and radial distribution of catalyst inside the downflow reactor. The radial distributor has equal numbers of stationary and movable parts placed one after another to cover the entire annular opening at the bottom of the regenerated catalyst vessel. The radial distributor is concentric with regenerator and located between the catalyst holding vessel and the reactor. A process for catalytic cracking using the invented apparatus is also disclosed.