This is a list of file formats used by computers, organized by type.
 Filename extensions are usually noted in parentheses if they differ from the file format name or abbreviation.
 Many operating systems do not limit filenames to one extension shorter than 4 characters, as was common with some operating systems that supported the File Allocation Table (FAT) file system.
 Examples of operating systems that do not impose this limit include Unix-like systems, and Microsoft Windows NT, 95, 98, and Me which have no three character limit on extensions for 32-bit or 64-bit applications on file systems other than pre-Windows 95 and Windows NT 3.5 versions of the FAT file system.
 Some filenames are given extensions longer than three characters.
Bare machine (or bare metal), in computer parlance, means a computer executing instructions directly on logic hardware without an intervening operating system.
 Modern operating systems evolved through various stages, from elementary to the present day complex, highly sensitive systems incorporating many services.
 After the development of programmable computers (which did not require physical changes to run different programs) but prior to the development of operating systems, sequential instructions were executed on the computer hardware directly using machine language without any system software layer.
 This approach is termed the "bare machine" precursor to modern operating systems.
 Today it is mostly applicable to embedded systems and firmware generally with time-critical latency requirements, while conventional programs are run by a runtime system overlaid on an operating system.
ACM SIGOPS is the Association for Computing Machinery's Special Interest Group on Operating Systems, an international community of students, faculty, researchers, and practitioners associated with research and development related to operating systems.
 The organization sponsors prestigious international conferences related to computer systems, operating systems, computer architectures, distributed computing, and virtual environments.
 In addition, the organization offers multiple awards recognizing outstanding participants in the field, including the Dennis M. Ritchie Doctoral Dissertation Award, in honor of Dennis Ritchie, co-creator of the renowned C programming language and Unix operating system.
Pedro Macedo Camacho (born September 4, 1979) is a Portuguese award-winning classical music, film and video game composer also known for his Requiem to Inês de Castro and his score for "Star Citizen".
These tables provide a comparison of operating systems, of computer devices, as listing general and technical information for a number of widely used and currently available PC or handheld (including smartphone and tablet computer) operating systems.
 The article "Usage share of operating systems" provides a broader, and more general, comparison of operating systems that includes servers, mainframes and supercomputers.
This is a list of operating systems with a sharp security focus.
 Here, "security-focused" means that the project is devoted to increasing the security as a major goal.
 As such, something may be secure without being "security-focused."
 For example, almost all of the operating systems mentioned here are faced with security bug fixes in their lifetime; however, they all strive consistently to approach all generic security flaws inherent in their design with new ideas in an attempt to create a secure computing environment.
 Security-focused does not mean security-evaluated operating system, which refers to operating systems that have achieved certification from an external security-auditing organization.
 An operating system that provides sufficient support for multilevel security and evidence of correctness to meet a particular set of government requirements is called a "trusted operating system".
A hypervisor or virtual machine monitor (VMM) is computer software, firmware or hardware that creates and runs virtual machines.
 A computer on which a hypervisor runs one or more virtual machines is called a "host machine", and each virtual machine is called a "guest machine".
 The hypervisor presents the guest operating systems with a virtual operating platform and manages the execution of the guest operating systems.
 Multiple instances of a variety of operating systems may share the virtualized hardware resources: for example, Linux, Windows, and macOS instances can all run on a single physical x86 machine.
 This contrasts with operating-system-level virtualization, where all instances (usually called "containers") must share a single kernel, though the guest operating systems can differ in user space, such as different Linux distributions with the same kernel.
Star Citizen is an upcoming massively multiplayer, space trading and combat video game for Microsoft Windows and Linux.
 The development includes a single-player campaign titled "Squadron 42".
The usage share of desktop operating systems is the percentage of the operating systems (OS) used in computers (approximately market share) with so-called (retronym) desktop operating system, that also run on e.g. laptops. Originally the only computers running those operating systems, where desktop computers, while with the introduction of so-called new class of mobile operating systems, desktop got to be the part of the name of the former class of OSes.
 The computers running these OSes have the desktop metaphor style of GUI, unlike the mobile OSes.
 See also usage share of operating systems for breakdown of the share of desktop, mobile (and other styles of) operating systems, separately, and share of those all operating systems as part of across classes.
Pedro Camacho (Pedro José Camacho Cotto; born 26 November 1938 in Santurce, Puerto Rico) is a Puerto Rican former triple jumper who competed in the 1960 Summer Olympics.

Question: For what operating systems is the game for which Pedro Camacho wrote the score?
Answer: Microsoft Windows and Linux