Common Intermediate Language (CIL), formerly called Microsoft Intermediate Language (MSIL) or Intermediate Language (IL),[1] is the intermediate language binary instruction set defined within the Common Language Infrastructure (CLI) specification.[2] CIL instructions are executed by a CLI-compatible runtime environment such as the Common Language Runtime (CLR). Languages which target the CLI compile to CIL. CIL is object-oriented, stack-based bytecode. Runtimes typically just-in-time compile CIL instructions into native code.