Glossary

This glossary lists common jargon you will frequently come across as you browse this wiki. Definitions you see below will appear in a popup when hovering on them in articles.

Hardware

 * AP  : Application Processor, the primary CPU of an Apple Silicon system-on-a-chip that most code executes on
 * ARM : The ARM instruction set used by the CPU and other coprocessors of an Apple Silicon system-on-a-chip
 * armv6: The ARM instruction set used by the CPU on early iOS devices
 * armv7: The ARM instruction set used by the CPU on early iOS devices
 * arm64: The ARM instruction set used by the CPU on current iOS devices
 * baseband: The modem chipset that provides cellular capabilities to a device
 * JTAG : An industry standard for testing hardware after manufacturing
 * NAND : "NOT-AND" logic gate, frequently used to refer to flash memory (solid-state drives)
 * NOR : "NOT-OR" logic gate, likely used to refer to the NOR flash memory used to hold boot data on early iOS devices
 * NVRAM: Non-volatile memory, used to store small amounts of data used during the boot process
 * S5L : The series of Samsung systems-on-a-chip used by iPods and early iOS devices, prior to A9
 * SEP : Secure Enclave Processor, a coprocessor on the system-on-a-chip that handles encryption requirements such Touch ID and Face ID
 * SoC : System on a chip, an integrated set of processors that provide the majority of an iOS device's core hardware functionality

Boot

 * bootrom
 * SecureROM: The first significant code that runs on an iOS device
 * DFU : Device Firmware Update mode, a feature of the bootrom allowing for emergency restores when the installed firmware is invalid
 * iBEC
 * iBootStage2: A stripped-down variant of iBoot, used to enter Restore Mode
 * iBoot: The bootloader on iOS devices and some later iPods, or a general name for the pre-kernel boot process
 * iBSS
 * iBootStage1: A stripped-down variant of iBoot, providing some services for the restore process
 * LLB : Low Level Bootloader, a component that runs setup routines before starting iBoot
 * Recovery Mode: The mode an iOS or later iPod device boots into when the operating system fails to boot, known by its "connect to computer" graphic
 * WTF : What's The Firmware, an early variant of DFU mode

Protocols

 * SWD : Serial Wire Debug, an electrical interface that can debug processors in a device
 * TSS : Tatsu Signing Server, the server that generates cryptographically signed strings that certifies that components of the boot process are allowed to run on the device

Firmware & Boot

 * APTicket: Application Processor Ticket, a cryptographically signed string that certifies that components of the boot process are allowed to run on the device
 * ASR : Apple System Restore, the program that installs a root filesystem image to a device
 * ECID : Exclusive Chip Identification, the serial number of an Apple Silicon system-on-a-chip
 * GM  : Golden Master, a dated term for a Release Candidate software version
 * IMG2 : File format used for images an early iOS or later iPod device can boot to
 * IMG3 : File format used for images later 32-bit iOS devices can boot to
 * IMG4
 * IM4P: File format used for images 64-bit iOS devices (including 32-bit Apple Watches) can boot to
 * IPSW : The file format that holds iOS and iPod firmware restore images
 * KBAG : A data format in the IMG3 and IMG4 formats that forms part of the decryption keys for encrypted firmware files
 * OTA : Over-the-air, often used to refer to OTA Updates, where an iOS device downloads and installs an update on itself without assistance from external hardware
 * ramdisk: A firmware image that contains a minimal operating system for certain tasks, named as such because it is stored temporarily in memory rather than permanently on disk
 * RC  : Release Candidate, a software version that is receiving final beta testing in anticipation of its official release.
 * RSR : Rapid Security Response, a mechanism allowing Apple to release urgent security updates without issuing a full OS release
 * SHSH : Signed hash, a cryptographically signed string that certifies that components of the boot process are allowed to run on the device

iTunes

 * AAS : Apple Application Support, a program consisting of the base libraries used by iTunes and other Apple apps on Windows
 * AMDS : Apple Mobile Device Support, a program consisting of libraries and a driver for iOS and iPod devices, used by iTunes, Xcode, and other Apple apps on macOS and Windows
 * QT  : The QuickTime media player, previously required for iTunes for audio/video playback

Security

 * CVE : Common Vulnerabilities and Exposures, a central database of security vulnerabilities reported in software