We present ASM Visualizer, a tool that is designed to help students learn assembly programming, aiding in their understanding of how assembly instructions are executed and the relationship between assembly and equivalent high-level language code. Our tool allows a user to step both forward and backward through the execution of an assembly program, one instruction at a time, seeing how instructions use and modify values in stack memory and CPU registers. ASM Visualizer presents three user-interface modes, supporting different stages of learning assembly programming. Beginners can step through basic arithmetic instructions, whereas more advanced learners can trace through function call/return sequences, stack frame manipulation, or entire assembly programs.

We present our experiences using ASM Visualizer in introductory level courses at our two institutions, and we discuss other ways in which our tool could be used by educators in both introductory and advanced CS courses. Results from a preliminary assessment of students using our tool show that students gain confidence in their understanding of different aspects of assembly programming. We feel that the visual interface to assembly code execution that ASM Visualizer provides is key to helping students understand assembly.