Engineering is the profession involved in designing, manufacturing, constructing, and maintaining of products, systems, and structures. With an initial aim of modernizing legacy systems, often written in old programming languages, software reverse engineering has now extended its applicability to virtually every kind of software system. Existing system's modification or replacement often applies reverse engineering for understanding of that system. Reverse engineering is nowadays used for more than one purpose that is sometimes illegal also. This paper presents an insight on this exciting and swiftly growing technology in the computer world.