emulation

Emulation is the process of reproducing the behavior of a computer system (the target) on another system (the host), enabling software and data designed for the target to run in a different environment. It aims to replicate the target’s processor instruction set, memory management, timing, and I/O to varying degrees of accuracy, often at the cost of performance.

Emulation supports preservation, compatibility, modernization, and research. It lets legacy software operate on current hardware and allows cross-platform development and testing. It differs from virtualization, which hosts a guest OS on the host processor without fully recreating the target hardware behavior; emulation seeks hardware-level fidelity.

Techniques include interpretation, where the emulator translates target instructions on the fly; dynamic recompilation or just-in-time translation, which translates code to host code for speed; and, in some cases, hardware-assisted virtualization or co-processors. Emulators may also replicate graphics, sound, and input devices to mirror expected behavior.

History and examples: Emulation has roots in arcade and mainframe preservation. Notable projects include MAME for arcade hardware, DOSBox for DOS, Dolphin for GameCube and Wii, and PCSX2 for PlayStation 2. General-purpose tools like QEMU provide full system emulation and virtualized environments.

Legal and ethical considerations center on software ownership and rights to firmware and ROM images. While creating emulators is legal in many jurisdictions, distributing copyrighted BIOS, game images, or other software without permission can violate law and license terms. Digital preservation often emphasizes documentation and licensing.