Glossary

Plain-English definitions of the terms you encounter when emulating retro games — cores, BIOS files, save states, shaders, mappers, and the rest.

14 terms

b

BIOS

A BIOS (Basic Input/Output System) is the firmware that ships baked into the original game console hardware — boot code, system menus, hardware initialization routines.
c

Cheat code

A cheat code in emulation is typically a short string (Game Genie, Pro Action Replay, or PAR format) that patches a specific memory address to a fixed value at runtime.
c

Core

In libretro / RetroArch terminology, a core is a single emulator implementation packaged as a shared library that conforms to the libretro API.
c

Cycle accuracy

A cycle-accurate emulator reproduces the original CPU's behavior on a per-clock-cycle basis, not just at a per-instruction level.
f

Frame pacing

Frame pacing is the consistency with which the emulator delivers a new frame to your display.
f

Frontend

A frontend is the host application that loads emulator cores, presents the game-selection UI, handles input bindings, and manages save data.
p

IPS / UPS patch

IPS and UPS are two binary patch formats used to ship ROM modifications without distributing the modified ROM itself.
m

Mapper

A mapper (or "memory mapper") is custom hardware on a game cartridge that bank-switches more ROM and RAM into the console's narrow address space than a flat layout could fit.
o

Overclocking

Emulator overclocking runs the emulated CPU faster than the original hardware, smoothing out games that suffer slowdown when many sprites or particles are on screen.
r

Rewind

Rewind is an emulator feature that lets you scrub backwards through the last few seconds (or minutes) of gameplay, undoing your last actions.
r

ROM

A ROM (Read-Only Memory image) is a binary copy of the contents of a game cartridge or disc.
s

Save file

A save file (or "in-game save") is the file the original cartridge / disc would have written to its battery-backed SRAM, memory card, or save chip.
s

Save state

A save state is a snapshot of the entire emulator memory (CPU registers, RAM contents, audio buffers, video state) written to disk in one atomic write.
s

Shader

A shader is a small GPU program that post-processes the emulator's output frame before it reaches your screen.