What is a runtime environment?

A runtime environment is an abstraction layer between code, the OS, and hardware that provides essential services so developers don't have to manage memory, CPU instructions, or networking protocols directly. Its key components include an execution engine (interpreter), runtime libraries (pre-written APIs), a memory management system (stack/heap allocation and garbage collection), and a core system interface for OS and hardware interaction. Web browsers are also runtime environments for frontend JavaScript, predating Node.js in most developers' experience.