Abstract: RISC-V has undergone rapid development and widespread adoption since its inception in 2010. It stands out among instruction set architectures not only for its relatively late launch, but more importantly for its fully open nature. As an emerging instruction set architecture, the architects of RISC-V have drawn extensive lessons from decades of various prior instruction set architectures. This paper presents the core design decisions of RISC-V, compares and analyzes the differences between RISC-V and traditional instruction set architectures, and thereby elaborates how RISC-V inherits the strengths of various architectures and avoids their inherent flaws.