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Other system components include:

About This Mac, which shows information about the Mac it is running on, such as the hardware, serial number, and macOS version.

Captive Network Assistant, a daemon used to access captive portals when connected to public Wi-Fi networks.

Certificate Assistant, a utility for creating and verifying digital certificates.

ControlStrip, a daemon that controls the Touch Bar.

CoreLocationAgent, a daemon responsible for displaying authorization prompts to allow apps and widgets to access location services.

Expansion Slot Utility, a program that allows manual allocation of PCIe card bandwidth. It is only available on certain Mac Pro models.

FolderActionsDispatcher, a daemon responsible for monitoring changes to the filesystem to run Folder Action scripts.

Install Command Line Developer Tools, a utility that allows developers to easily install Xcode's command line developer tools if Xcode is not installed. It can be executed by running xcode-select --install in the terminal.

iOS App Installer, an app that downloads .ipa files for iPadOS applications so that they can be run on Apple silicon-based Macs.

Keychain Circle Notification, a daemon involved in iCloud Keychain syncing.

ManagedClient manages various functions pertaining to managed preferences and configuration profiles.

Setup Assistant is the application that starts on first boot of a fresh copy of macOS or a new Mac. It configures computer accounts, Apple ID, iCloud, and Accessibility settings. It is also run after major macOS system upgrades.

OBEXAgent, a server that handles Bluetooth access.

ODSAgent, a server that handles remote disk access.

OSDUIHelper, a daemon that displays on-screen graphics when certain settings, such as volume or display brightness, are adjusted.

PIPAgent, which manages the picture-in-picture feature available in macOS Sierra and later.

Photo Library Migration Utility, which can migrate iPhoto and Aperture libraries to Photos.

PowerChime, present on some MacBook models, plays a chime when the notebook is plugged in to power.

ReportPanic, an app that displays a window when the system reboots from a kernel panic; it allows the user to send a report to Apple.

screencaptureui, a daemon responsible for drawing the user interface shown when taking a screenshot.

ScreenSaverEngine, the process that handles screen saver access. When invoked, it will display the screensaver.

SystemUIServer, a daemon that manages status items in the menu bar.

ThermalTrap, a daemon which notifies users when the system temperature exceeds a usable limit.

Ticket Viewer, an app that displays Kerberos tickets.

UnmountAssistantAgent, which displays a dialog if there is a process preventing ejection of a disk and offers to forcibly eject the disk if the process cannot be quit.

Wireless Diagnostics, an app that launches when Wi-Fi connectivity problems are detected.

Classic

The Classic Environment, usually referred to as Classic, is a hardware and software abstraction layer in PowerPC versions of Mac OS X that allows most legacy applications compatible with Mac OS 9 to run on Mac OS X. The name "Classic" is also sometimes used by software vendors to refer to the application programming interface available to "classic" applications, to differentiate between programming for Mac OS X and the classic version of the Mac OS.

The Classic Environment is supported on PowerPC-based Macintosh computers running versions of Mac OS X up to 10.4 "Tiger", but not with 10.5 "Leopard" or Macintoshes utilizing any other architecture than PowerPC.

The Classic Environment is a descendant of Rhapsody's "Blue Box" virtualization layer, which served as a proof of concept. (Previously, Apple A/UX also offered a virtualized Mac OS environment on top of a UNIX operating system.) It uses a Mac OS 9 System Folder, and a New World ROM file to bridge the differences between the older PowerPC Macintosh platforms and the XNU kernel environment. The Classic Environment was created as a key element of Apple's strategy to replace the classic Mac OS (versions 9 and below) with Mac OS X as the standard operating system (OS) used by Macintosh computers by eliminating the need to use the older OS directly.

The Classic Environment can be loaded at login (for faster activation when needed later), on command, or whenever a Mac OS application that requires it is launched (to reduce the use of system resources when not needed). It requires a full version of Mac OS 9 to be installed on the system, and loads an instance of that OS in a sandbox environment, replacing some low-level system calls with equivalent calls to Mac OS X via updated system files and the Classic Support system enabler. This sandbox is used to launch all "classic" Mac OS applications—there is only one instance of the Classic process running for a given user, and only one user per machine may be running Classic at a time.

The Classic Environment can also be configured to show a window upon startup of the Classic Environment to simulate a computer booting into Mac OS 9. If the user chooses to launch the Classic Environment only when needed, launching a "classic" application first launches the Classic Environment, and then the application launches. When a "classic" application is in the foreground, the menu bar at the top of the screen changes to the older-style Mac OS menu bar. Dialog boxes and other user-interface elements retain their traditional appearance.

The Classic Environment also provides a way to run "Classic" applications on Apple's G5 systems as well as on most G4 based computers sold after January 2003. These machines cannot boot Mac OS 9 or earlier without the bridging capabilities of the Classic Environment or other software (see SheepShaver); in the former case, G5 Macs cannot run Mac OS 9 natively due to the lack of G5 processor support on Mac OS 9, while in the latter case, G4 Macs released from that point onwards cannot boot into Mac OS 9 natively because the "Mac OS ROM" boot files were not updated to support booting into Mac OS 9 directly from those Macs.

The Classic Environment's compatibility is usually sufficient for many applications, provided the application using it does not require direct access to hardware or engage in full-screen drawing. However, it is not a complete clone of Mac OS 9. The Finder included with Mac OS X v10.2 and later does not support the "Reveal Object" Apple events used by some Mac OS 9 applications, causing the "Reveal In Finder" functionality for those applications to be lost. Early releases of Mac OS X would often fail to draw window frames of Classic applications correctly, and after the Classic Environment's windowing was made double buffered in Mac OS X Panther, some older applications and games sometimes failed to update the screen properly, such as the original Macintosh port of Doom. On the other hand, the Classic Environment also "resurrected" some older applications that were previously made unusable on the Macintosh Quadra and Power Macintosh series; this is because Mac OS X replaced Mac OS 9's original virtual memory system with a more standard and less fragile implementation.

The Classic Environment's performance is also generally acceptable, with a few exceptions. Most of an application is run directly as PowerPC code (which would not be possible on Intel-based Macs). Motorola 68k code is handled by the same Motorola 68LC040 emulator that Mac OS 9 uses. Some application functions are actually faster in the Classic Environment than under Mac OS 9 on equivalent hardware, due to performance improvements in the newer operating system's device drivers. These applications are largely those that use heavy disk processing, and were often quickly ported to Mac OS X by their developers. On the other hand, applications that rely on heavy processing and which did not share resources under Mac OS 9's co-operative multitasking model will be interrupted by other (non-Classic) processes under Mac OS X's preemptive multitasking. The greater processing power of most systems that run Mac OS X (compared to systems intended to run Mac OS 8 or 9) helps to mitigate the performance degradation of the Classic Environment's virtualization.

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