Operating systems

Definitions related to operating systems, including tech terms about open source and proprietary operating systems and words and phrases about system programs, boot mechanisms, kernels, command interpreters, DLL libraries and drivers.
  • .NET Framework - .NET Framework is a managed execution environment for Windows that allows software developers to create a software application in one programming language and be assured the app can work with code written in other languages.
  • 99.999 (Five nines or Five 9s) - In computers, 99.
  • access control list (ACL) - An access control list (ACL) is a list of rules that specifies which users or systems are granted or denied access to a particular object or system resource.
  • Active Directory domain (AD domain) - An Active Directory domain (AD domain) is a collection of objects within a Microsoft Active Directory network.
  • Active Directory Federation Services (AD FS) - Active Directory Federation Services (AD FS) is a feature of the Windows Server operating system (OS) that extends end users' single sign-on (SSO) access to applications and systems outside the corporate firewall.
  • Active Directory functional levels - Active Directory functional levels are controls that specify which advanced Active Directory domain features can be used in an enterprise domain.
  • Android Open Source Project (AOSP) - The Android Open Source Project (AOSP) is the repository of source code and the foundation which maintains it that is responsible for the core of the Android operating system.
  • Android OS - Android OS is a Linux-based mobile operating system that primarily runs on smartphones and tablets.
  • Apple iOS - Apple iOS is a proprietary mobile operating system that runs on mobile devices such as the iPhone and iPad.
  • AS/400 (IBM iSeries, AS/400e, eServer iSeries/400, Power Systems) - The IBM Application System/400 -- or AS/400 -- is a family of midrange computers that was released in 1988, succeeding both System/36 and System/38 platforms.
  • attribute - In general, an attribute is a property, quality, or characteristic that something or someone has.
  • Automatic Private IP Addressing (APIPA) - Automatic Private IP Addressing (APIPA) is a feature of Windows-based OSes -- included since Windows 98 and Windows ME -- that enables a Dynamic Host Configuration Protocol client to automatically assign an IP address to itself when there's no DHCP server available to perform that function.
  • bash (Bourne again shell) - Bash (Bourne Again Shell) is the free and enhanced version of the Bourne shell distributed with Linux and GNU operating systems.
  • beep code - A beep code is the audio signal from a computer when it first powers on to give the Power-On Self-Test (POST) result.
  • binary - Binary describes a numbering scheme in which there are only two possible values for each digit -- 0 or 1 -- and is the basis for all binary code used in computing systems.
  • BIOS (basic input/output system) - BIOS (basic input/output system) is the program a computer's microprocessor uses to start the computer system after it is powered on.
  • board support package - A board support package (BSP) is essential code code for a given computer hardware device that will make that device work with the computer's OS (operating system).
  • boot - To boot (to boot up, to start up or booting) a computer is to load an operating system (OS) into the computer's main memory or random-access memory (RAM).
  • boot loader (boot manager) - A boot loader (boot manager) is a small program that places the operating system (OS) of a computer into memory.
  • Bourne shell - The Bourne shell is the original Unix shell -- command execution program, often called a command interpreter -- that was developed in 1979 at what at the time was Bell Labs.
  • C shell - C shell (csh) is a Unix shell that provides a command-line user interface (UI) to interact with an operating system (OS).
  • CICS (Customer Information Control System) - CICS (Customer Information Control System) is middleware that sits between the z/OS IBM mainframe operating system and business applications.
  • clean install - A clean install is a software installation in which any previous version is eradicated.
  • cold backup (offline backup) - A cold backup is a backup of an offline database.
  • command-line interface (CLI) - A command-line interface (CLI) is a text-based user interface (UI) used to run programs, manage computer files and interact with the computer.
  • Conficker - Conficker is a fast-spreading worm that targets a vulnerability (MS08-067) in Windows operating systems.
  • CONFIG.SYS - CONFIG.SYS is a text file containing disk operating system (DOS) commands that tell the operating system (OS) how the computer is initially set up.
  • context switch - A context switch is an operation that a computer's central processing unit (CPU) carries out when alternating between processes or threads while ensuring that the processes do not conflict.
  • COTS, MOTS, GOTS and NOTS - COTS, MOTS, GOTS and NOTS are abbreviations that describe prepackaged software or -- less commonly -- hardware purchase alternatives.
  • Ctrl-Alt-Delete - On a personal computer with the Microsoft Windows operating system, Control+Alt+Delete is the combination of the Ctrl key, the Alt key, and Del key that a user can press at the same time to terminate an application task or to reboot the operating system.
  • cursor - A cursor is the position indicator on a computer display screen where a user can enter text.
  • Cygwin - Cygwin is a collection of open source tools that allows Unix or Linux applications to be compiled and run on a Microsoft Windows operating system (OS) from within a Linux-like interface.
  • deadlock - A deadlock is a situation in which two computer programs sharing the same resource are effectively preventing each other from accessing the resource, resulting in both programs ceasing to function.
  • Debian - Debian is a popular and freely available computer operating system (OS) that uses a Unix-like kernel -- typically Linux -- alongside other program components, many of which come from GNU Project.
  • defragmentation - Defragmentation is the process of locating the noncontiguous fragments of data into which a computer file may be divided as it is stored on a hard disk, and rearranging the fragments and restoring them into fewer fragments or into the whole file.
  • Distributed Component Object Model (DCOM) - Distributed Component Object Model (DCOM) is an extension to Component Object Model (COM) that enables software components to communicate with each other across different computers on a local area network (LAN), on a wide area network (WAN) or across the internet.
  • Eclipse (Eclipse Foundation) - Eclipse is a free, Java-based development platform known for its plugins that allow developers to develop and test code written in other programming languages.
  • embedded hypervisor - An embedded hypervisor is a hypervisor that is programmed (embedded) directly into a processor, personal computer (PC) or server.
  • Extended Binary Coded Decimal Interchange Code (EBCDIC) - Extended Binary Coded Decimal Interchange Code (EBCDIC) is an eight-bit encoding scheme that standardizes how alphanumeric characters, punctuation and other symbols are interpreted by a computer's operating system (OS) and applications.
  • failover - Failover is a backup operational mode in which the functions of a system component are assumed by a secondary component when the primary becomes unavailable.
  • fault tolerance - Fault tolerance is the capability of a system to deliver uninterrupted service despite one or more of its components failing.
  • Fedora - Fedora, also known as Fedora Linux, is a popular open source Linux-based operating system (OS).
  • File Allocation Table (FAT) - File Allocation Table (FAT) is a file system that Microsoft developed to support small disks and simple folder structures.
  • file extension (file format) - In computing, a file extension is a suffix added to the name of a file to indicate the file's layout, in terms of how the data within the file is organized.
  • file sharing - File sharing is the public or private sharing of files or folders on a networked computer.
  • file system - In computing, a file system -- sometimes written filesystem -- is a logical and physical system for organizing, managing and accessing the files and directories on a device's solid-state drive (SSD), hard-disk drive (HDD) or other media.
  • font - The word 'font' refers to a set of printable or displayable typography or text characters in a specific style and size.
  • GID (group ID or global index file) - In a Unix system, a GID (group ID) is a name that associates a system user with other users sharing something in common (perhaps a work project or a department name).
  • GNU Project - The GNU Project is a mass collaborative initiative for the development of free software, specifically a free operating system called GNU.
  • GNU/Linux - GNU/Linux is a Unix-like operating system made up of different OS components and services that create the Linux OS.
  • Google Android 4.4 KitKat - Android 4.4 KitKat is a version of Google's operating system (OS) for smartphones and tablets.
  • Google Chrome Enterprise - Google Chrome Enterprise is the business-focused solution for Chrome devices, Chrome browser and Chrome OS.
  • Google ChromeOS - Google ChromeOS, formerly Chrome OS, is a lightweight operating system (OS) built on ChromiumOS, an open source OS that shares the same code base as ChromeOS.
  • guest virtual machine (guest VM) - A guest virtual machine (VM) is the software component of a VM, an independent instance of an operating system (OS), called a guest OS, and its associated software and information.
  • hypervisor - A hypervisor is software that facilitates running multiple virtual machines (VMs) with their own operating systems on a single computer host's hardware.
  • IBM Roadrunner - Roadrunner was a supercomputer developed by IBM at the Los Alamos National Laboratory in New Mexico.
  • icon - In today's age of technological advancement, most people recognize the word 'icon' as referring to a small selectable or nonselectable image representing or leading to something else in a computer's graphical user interface (GUI) or on the web.
  • initial program load (IPL) - IPL (initial program load) is a mainframe term for the loading of the operating system into the computer's main memory.
  • IO.SYS - IO.SYS is a hidden executable binary file that processes instructions that tell the operating system (OS) how the computer is set up when it is booted or started.
  • ITAR and EAR compliance - The International Traffic in Arms Regulations (ITAR) and the Export Administration Regulations (EAR) are two important U.
  • job - In certain computer operating systems, a job is the unit of work that a computer operator -- or a program called a job scheduler -- gives to the OS.
  • job step - In certain computer operating systems, a job step is part of a job, a unit of work that a computer operator (or a program called a job scheduler) gives to the operating system.
  • kiosk mode (Windows assigned access) - Kiosk mode is a feature in Windows operating system (OS) that allows a device to run only specified applications and settings.
  • lights-out management (LOM) - Lights-out management (LOM) is a form of out-of-band management.
  • Linux operating system - Linux is a Unix-like, open source and community-developed operating system (OS) for computers, servers, mainframes, mobile devices and embedded devices.
  • Linux swappiness - Linux swappiness is a kernel parameter that determines how aggressively the Linux virtual machine (VM) swaps pages between memory and the swap space on the system's disk.
  • Local Group Policy Editor - Local Group Policy Editor is a Microsoft Management Console (MMC) snap-in that provides a user interface for managing local Group Policy settings on a Windows computer.
  • logical partition (LPAR) - A logical partition (LPAR) is a subset of a computer's processor, memory and I/O resources that behaves much like a physical server.
  • macOS - MacOS is the computer operating system for Apple desktops and laptops.
  • Master Boot Record (MBR) - The Master Boot Record (MBR) is the information in the first sector of a hard disk or a removable drive.
  • menu - A menu is a set of options presented to the user of a computer application to help them find information or execute a function.
  • Microsoft - Microsoft is the largest vendor of computer software in the world.
  • Microsoft Windows Hello - Microsoft Windows Hello is a biometric identity and access control feature that supports fingerprint scanners, iris scanners and facial recognition technology on compatible devices running Windows.
  • Microsoft Windows Recovery Environment (Windows RE) - The Microsoft Windows Recovery Environment, or Windows RE, is a simplified, scaled-back version of the Windows operating system that is used to boot the system when Windows 8.
  • Microsoft Windows Server 2016 - Microsoft Windows Server 2016 is Microsoft's server operating system (OS).
  • Microsoft Windows Server LTSC (Long-Term Servicing Channel) - Microsoft Windows Server LTSC (Long-Term Servicing Channel) is one of the servicing options available for users of the Windows Server operating system (OS).
  • mobile operating system - A mobile operating system (OS) is software that allows smartphones, tablet PCs (personal computers) and other devices to run applications and programs.
  • MPP (massively parallel processing) - MPP (massively parallel processing) is the coordinated processing of a program by multiple processors that work on different parts of the program, with each processor using its own operating system and memory.
  • MS-DOS (Microsoft Disk Operating System) - MS-DOS (Microsoft Disk Operating System) was the Microsoft-marketed version of the first widely-installed operating system in personal computers.
  • Nagios - Nagios is an open source IT system monitoring tool.
  • network operating system (NOS) - A network operating system (NOS) is a computer operating system (OS) that's designed primarily to support workstations, PCs and, in some instances, older terminals that are connected on a local area network (LAN).
  • operational-level agreement (OLA) - An operational-level agreement (OLA) is a contract that defines how various IT groups within a company plan to deliver a service or set of services.
  • Opex (operational expenditure) - Opex (operational expenditure) is the money a company or organization spends on an ongoing, day-to-day basis to run its business.
  • OS X - OS X, also referred to as macOS X or Mac OS X, is Apple's proprietary, Unix-based operating system.
  • Patch Tuesday - Patch Tuesday is the unofficial name of Microsoft's monthly scheduled release of security fixes for the Windows operating system (OS) and other Microsoft software.
  • performance testing - Performance testing is a testing measure that evaluates the speed, responsiveness and stability of a computer, network, software program or device under a workload.
  • pipe - In computer programming, especially in Unix operating systems (OSes), a pipe is a technique for passing information from one program process or command to another.
  • POSIX (Portable Operating System Interface) - POSIX (Portable Operating System Interface) is a set of standard operating system interfaces based on the Unix operating system.
  • POST (Power-On Self-Test) - A Power-On Self-Test (POST) is an operation initiated by a computer after it has been turned on but before it boots up the OS.
  • PowerFlex (formerly ScaleIO) - PowerFlex is a software-defined storage product from Dell EMC.
  • principle of least privilege (POLP) - The principle of least privilege (POLP) is a concept in computer security that limits users' access rights to only what is strictly required to do their jobs.
  • process - A process is an instance of a program running in a computer.
  • race condition - A race condition is an undesirable situation that occurs when a device or system attempts to perform two or more operations at the same time, but because of the nature of the device or system, the operations must be done in the proper sequence to be done correctly.
  • Red Hat Enterprise Linux (RHEL) - Red Hat Enterprise Linux (RHEL) is an enterprise Linux operating system (OS) developed by Red Hat for the business market.
  • restore point - A system restore point is a backup copy of important Windows operating system (OS) files and settings that can be used to recover the system to an earlier point of time in the event of system failure or instability.
  • runlevel - A runlevel is an operating state on a Unix and Unix-based operating system that is preset on the Linux-based system.
  • security identifier (SID) - In the context of Windows computing and Microsoft Active Directory (AD), a security identifier (SID) is a unique value that is used to identify any security entity that the operating system (OS) can authenticate.
  • shell program - A shell program is software that provides users with an interface for accessing services in the kernel.
  • software - Software is a set of instructions, data or programs used to operate computers and execute specific tasks.
  • sudo (su 'do') - Sudo is a command-line utility for Unix and Unix-based operating systems such as Linux and macOS.