Mac OS X
Overview & Glossary

Updated: 6-22-01

Information provided by: Andrea Barr

X Overview

Application Environments

Application Services

Core Services



application environment
Consists of the frameworks, libraries, and services (along with associated APIs) necessary for the runtime execution of programs developed with those APIs. The application environments have dependencies on all underlying layers of system software. Mac OS X currently has five application environments: Classic, Carbon, Cocoa, Java, and BSD Commands.

application programming interface (API)
A set of routines used by an application to direct the performance of procedures by the computer's operating system.

A term used to describe the Mac OS X user interface, chosen because it means "water" in many languages and the characteristics of water infuse the user experience of Mac OS X.

Berkeley Software Distribution (BSD)
Formerly known as "the Berkeley version" of UNIX, BSD is now simply called the BSD operating system. The BSD portion of Mac OS X is based on 4.4BSD Lite 2 and FreeBSD, a "flavor" of 4.4BSD.

An application environment that provides Mac OS 9 applications with all the features of Darwin, including protected memory for crash-resistant computing and preemptive multitasking for a more responsive system, as well as the new Aqua look and feel.

Carbon features a set of programming interfaces derived from earlier versions of the Mac OS. The Carbon APIs have been modified to work properly with Mac OS X, especially with the foundation of the operating system, the kernel environment.

Carbon applications can run on Mac OS X, Mac OS 9, and all versions of Mac OS 8 later than Mac OS 8.1.

An application environment that allows users to continue to use their systems for everything they already do. Classic applications don't appear in the new Aqua interface.

Classic supports programs built for both PowerPC and 68K chip architectures and is fully integrated with the Finder and the other application environments in Mac OS X.

An advanced object-oriented programming environment for building new next-generation applications.

Cocoa is a set of frameworks with programming interfaces in both Java and Objective-C. It is based on the integration of OpenStep, Apple technologies, and Java.

Another name for the Mac OS X core operating system, which includes some, but not all, of the components of Mac OS X.

The Darwin kernel is equivalent to the Mac OS X kernel plus the BSD libraries and commands essential to the BSD Commands environment. Darwin is open source technology.

Domain Name Services (DNS)
The standard Internet service for mapping host names to IP addresses.

Dynamic Host Configuration (DHCP)
Automates the assignment of IP addresses in a particular network.

file system
Refers to the way in which files are named and where they are placed logically for storage and retrieval. In Mac OS X, files are placed in a hierarchical tree structure, either in directories or subdirectories.

File Transfer Protocol (FTP)
A standard means of moving files between computers on TCP/IP networks.

Hypertext Transport Protocol (HTTP)
The standard protocol for transferring web pages between a web server and browser.

The design or modification of a software product, including online help and documentation, to facilitate localization. Internationalization of software typically involves writing or modifying code to make use of locale-aware operating-system services for appropriate localized text input, display, formatting, and manipulation. See also localization.

The complete Mac OS X core operating-system environment, which includes Mach, BSD, the I/O Kit, file systems, and networking components. Also called the kernel environment.

Lightweight Directory Access Protocol (LDAP)
Lets users locate organizations, individuals, and resources such as files and devices in a network, whether on the Internet or on a corporate intranet.

The adaptation of a software product, including online help and documentation, for use in one or more regions of the world, in addition to the region for which the original product was created. Localization of software can include translation of user-interface text, resizing of text-related graphical elements, and replacement or modification of user-interface images and sound. See also internationalization.

The lowest level of the Mac OS X kernel. Mach provides such basic services and abstractions as threads, tasks, ports, interprocess communication (IPC) scheduling, physical and virtual address space management, virtual memory, and timers.

memory protection
A system of memory management in which programs are prevented from being able to modify or corrupt the memory partition of another program. Mac OS 8 and Mac OS 9 do not have memory protection; Mac OS X does.

The concurrent execution of multiple programs. Mac OS X uses preemptive multitasking. Mac OS 8 and Mac OS 9 use cooperative multitasking.

A pane in System Preferences used to enter settings to connect to a network, and an icon users see when they click the Computer button in a Finder window.

Also, a group of hosts that can directly communicate with each other.

Network File System (NFS)
An NFS file server allows users on the network to share files on other hosts as if they were on their own local disks.

Network Time Protocol (NTP)
Used for synchronizing client clocks.

open source
A definition of software that includes freely available access to source code, redistribution, modification, and derived works. The full definition is available at

Point-to-Point Protocol (PPP)
A protocol for dialup (modem) access. PPP support includes TCP/IP as well as the PAP and CHAP authentication protocols.

Portable Operating System Interface (POSIX)
An operating-system interface standardization effort supported by ISO/IEC, IEEE, and The Open Group.

The act of interrupting a currently running task in order to give time to another task.

preemptive multitasking
A type of multitasking in which the operating system can interrupt a currently running task in order to run another task, as needed.

Printer Access Protocol (PAP)
Printer Access Protocol. Used for spooling print jobs and printing to network printers.

serial transmission
Supports modem, DSL, and ISDN capabilities.

Service Location Protocol (SLP)
A protocol designed for the automatic discovery of resources (printers, servers, fax machines, and so on) on an IP network.

symmetric multiprocessing (SMP)
A feature of an operating system in which two or more processors are managed by one kernel, sharing the same memory, having equal access to I/O devices, and in which any task, including kernel tasks, can run on any processor.

10/100BASE-T Ethernet
The network connection type built into every new Macintosh. An IEEE standard for data transmission over fiber-optic cable and standardized copper wiring.

10/100/1000BASE-T Ethernet
The IEEE standard for data transmission over an Ethernet network at rates over 1,000 megabits (Mbps) per second. Also known as Gigabit Ethernet.

Transmission Control Protocol (TCP/IP)
A transmission-layer protocol designed to work with the network-layer Internet Protocol (IP).

User Datagram Protocol (UDP/IP)
A transmission-layer protocol designed to work with the network-layer Internet Protocol (IP).

virtual memory (VM)
The use of a disk partition or a file on disk to provide the same facilities usually provided by RAM. The virtual-memory manger in Mac OS X provides 32-bit (minimum) protected address space for each task and facilitates efficient sharing of that address space.

A 16-bit character encoding standard developed by the Unicode Consortium between 1988 and 1991. By representing two bytes to represent each character, Unicode enables almost of the written languages of the world to be represented using a single character set.