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    An operating system (OS) is a software program that serves as the interface between other applications and the hardware on a computer or mobile device.

    What does an operating system do?

    Desktop operating systems perform basic tasks, such as recognizing input from a keyboard, sending output to a display screen, managing files and directories on a storage drive, and controlling peripheral devices like printers. Operating systems on larger devices can also support many advanced operations, including multitasking, multi-user management, multiprocessing, and multithreading.


    The early computers that were used in the 1940s and 1950s did not have any operating system. They were just mainframe computers used for processing data. The computer was operated using a combination of panel lights, dials, and toggle switches. Data would be loaded into the computer using paper tape, magnetic tape, or paper cards. The computer would process the data until the task gets completed or the computer crashes. As hardware systems evolved into more advanced computers capable of handling more complex data, there was a need for an operating system for the computers.

    In the 1960s, the Atlas Supervisor was created to manage the processing of allocation resources for the Atlas Computer at Manchester University. The Atlas Supervisor is considered by many to be the first modern computer operating system. By the 1970s, General Motors had created the NAA I/O operating system and Bell Labs had developed the UNIX operating system. These were followed by the development of the Apple II series in 1977 by the famous micro-computer designer Steve Wozniak.

    The computer operating system evolved rapidly through the 1980s and 1990s to the operating system we are using in the modern world. This includes the Windows operating systems and Macintosh operating systems, which are two of the most commonly used operating systems in the modern world.

    Functions of an operating system

    Although some operating systems offer unique features or designs, most have a consistent set of functions at their core:

    • The user interface, either a graphical user interface (GUI) or a command-line interface (CLI), provides a way for users to interact with the operating system and perform operations outside of an application. The primary difference between these types of user interfaces is that a CLI uses a text-based terminal, whereas a GUI provides a visual desktop with icons and virtual buttons.
    • The software platform is what gives application programs the foundation to operate. In most cases, an operating system launches and maintains the applications, facilitates the input to and output from the hardware, and manages the resources being used to run the application. These applications can also send requests for the operating system to perform specific tasks using an application program interface (API).
    • The kernel provides base-level management of a device’s underlying hardware. This includes the central processing unit (CPU), memory, USB ports, graphics devices, and storage devices.

    Types of Operating Systems

    Real-Time Operating System (RTOS)

    The RTOS is used for real-time applications such as missile systems, robots, and air traffic control systems. With this type of operating system, there are strictly defined time constraints. The response time of RTOS is very small compared to other types of operating systems. The advantages of RTOS include optimum handling of system resources and minimized task shifting with a focus on running applications.

    Time-Sharing Operating System

    In the time-sharing operating system, also referred to as a multitasking system, each task is provided time to complete its execution. The tasks can be from multiple users or single users. The advantages of this type of operating system are that each task gets an equal opportunity and computer processing idle time is reduced.

    Distributed Operating System

    In this type of operating system, interconnected computers communicate with each other on a shared network. In a type of loosely coupled system, the distributed operating system can harness the resources of several computers to perform a single task or multiple tasks.

    Network Operating System

    Network operating systems are run on servers such as the Microsoft Windows Server and the Mac OS X. The advantage of this type of operating system is that they are backed by highly stable centralized servers that offer remote access and data backup features.

    Desktop operating systems

    Most devices come with an operating system already preloaded. As such, the operating system a device has depends on the hardware manufacturer. A desktop or laptop computer will typically use one of the following operating systems:

    • Microsoft Windows represents the largest share of operating systems in use today. Microsoft distributes Windows across its line of Surface devices and also licenses the software to almost all PC manufacturers including Dell, HP, Lenovo, Asus, and Acer.
    • macOS (formerly Mac OS X) is the operating system exclusive to Apple devices. Famous for its closed architecture designs, Apple developed macOS to run exclusively on its collection of Mac laptops and desktops.
    • Linux is an open-source operating system that’s freely distributed for a number of hardware platforms. The Linux OS family was developed in the 1990s as a derivative of the commercial UNIX operating system.

    Mobile operating systems

    Most mobile devices, from smartphones to tablets to smartwatches, have dedicated operating systems that provide unique functionalities. Because these devices are usually smaller and offer limited resources, the operating systems prioritize efficiency and responsiveness. Popular developers for mobile device operating systems include:

    • Apple has developed separate operating systems for each of its mobile devices: iOS for iPhone, iPadOS, and watchOS. Alongside macOS, each of these operating systems leverage iCloud to create a seamless user experience across devices.
    • Microsoft, which included support for tablets in its 2015 release of Windows 10.
    • Google, whose Android operating system dominates the market for tablets and smartphones. Amazon’s line of Fire tablets use an adapted version of the Android software, called Fire OS, that maintains most of the core features but has a heavier focus on Amazon services like Prime Video, Amazon Music, Kindle, and Audible.

    Real-time operating systems

    Some operating systems are embedded in devices that serve a niche purpose, like medical devices, automated teller machines (ATMs), and smart home devices. These operating systems are called real-time operating systems (RTOS) because they perform actions within a set amount of time and process data as soon as it’s received. An RTOS is generally much lighter than a mobile or desktop operating system, so it’s developed to execute a limited number of operations with high efficiency and reliability.

    This article was reviewed and updated in April 2022 by Ali Azhar.