When we hear about operating systems, we usually think automatically of computers and the software that appears a few seconds after turning them on . However, the role of an operating system goes far beyond the desktop PC: it's in mobile phones, tablets, smart TVs, routers, and even cars. Without it, any of these devices would be little more than a collection of useless electronic components.
Despite being so essential, the functions of an operating system often go unnoticed. Understanding what they actually do, what types exist, and what their key characteristics are in environments like Windows , Linux, macOS, or Android is fundamental if you have even a basic understanding of the world of computing or if you're considering studying something related, such as Computer Systems Administration or a degree in Computer Science.
What is an operating system and why is it so important?
An operating system (OS) is the core software that controls and coordinates everything that happens on an electronic device . It acts as an intermediary between the hardware (CPU, memory, disk, screen, keyboard, mouse, printer, etc.) and the programs that the user runs (browser, text editor, video game, messaging app, etc.).
Without this intermediary software, the user would have to speak the hardware's "language" directly and know in detail how each component works. The operating system translates these commands so we can interact with the device through a graphical or command-line interface , without having to worry about what's happening "behind the scenes."
In practice, the operating system defines the basic operating protocol of the computer: how memory is managed, how the disk is accessed, how programs communicate, what permissions each user has, and what happens when an input/output (I/O) device needs attention. This is why it is considered the core software of any computer system.
Operating systems are also sometimes known as the "kernel," although strictly speaking the kernel is only the innermost part responsible for resource management, while the complete operating system includes more layers and utilities that provide the user's working environment.
General characteristics of a modern operating system
Although each operating system has its own philosophy and design, most share a set of essential features that allow for their effective use on computers, mobile devices, or servers. Among the most important are the following:
First, an operating system acts as an intermediary between the user and the hardware . It's the bridge that translates simple actions like clicking an icon or pressing a key into commands that the CPU, memory, or graphics card can understand.
It is also an essential component for the operation of any general-purpose device . A PC, tablet, or smartphone without an operating system could not boot into a usable environment because there would be nothing "orchestrating" the different resources.
Another key feature is its role in security and the protection of data and applications. The operating system implements user authentication mechanisms, permission control, process isolation, data encryption, and security patch updates to minimize vulnerabilities and unauthorized access.
It is also designed with usability in mind. Most current operating systems offer intuitive graphical interfaces, desktops, menus, and windows that allow non-expert users to operate the device with relative ease, without needing to resort to a command line except for advanced tasks.
On the other hand, efficient resource management is one of its main missions. A good operating system manages the CPU, main memory, I/O devices, and secondary storage in a way that maximizes the hardware's capabilities, avoiding bottlenecks and unnecessary freezes.
In many cases, the use of the operating system is subject to commercial licenses (such as Windows or some editions of macOS in closed environments). Others, such as Linux, are distributed under free software licenses that allow their use, modification, and redistribution at no cost.
Finally, modern operating systems are constantly evolving through updates . These new versions or patches improve performance, add features, fix bugs, and strengthen security against new threats.
Basic components of the operating system
Although from the outside we may see it as a single program, an operating system is made up of several components or software packages that work together. Among the most important elements are:
The first is the kernel , the heart of the operating system. It is directly responsible for critical tasks such as communication with the hardware, process management, memory control, interrupt handling, and CPU scheduling. It typically runs in privileged mode, with access to all processor instructions.
Secondly, there is the file system , which defines how data is organized and stored on disks and other persistent media. Thanks to it, files are structured into folders or directories, access permissions are controlled, and data integrity is ensured as much as possible.
Also fundamental are the components responsible for command interpretation and the user interface. These can be command-line interpreters (like bash in Linux) or graphical desktop environments (like Explorer in Windows or Finder in macOS). Their function is to translate user actions into requests to the kernel and the various system services.
Around these basic blocks are grouped other modules and services, such as device drivers , which allow the operating system to communicate with specific peripherals (printers, network cards, cameras, etc.), or interface libraries, which make it easier for programmers to use system calls without having to know the low-level details.
Types of operating systems according to their approach
Operating systems can be classified according to several criteria: the type of device they are designed for, the number of users they support, how they manage tasks, or how they administer resources. The most common groups are the following.
According to the device: desktop, mobile, server and embedded
Within this category, we first find desktop operating systems , designed for personal computers, both laptops and desktops. Their best-known representatives are Windows, macOS, and the various Linux distributions. They are designed to work with multiple applications, offer a complete desktop environment, and integrate a wide variety of peripherals.
Secondly, there are mobile operating systems , which power smartphones, tablets, and other touch devices. Android and iOS are the dominant players in this segment, although there are others like iPadOS, watchOS, and proprietary systems such as Xiaomi's HyperOS for some devices. Their goal is to offer a simple, touch-based experience that is highly optimized for battery life.
Another key group is server operating systems . These are installed on machines that serve many users simultaneously (web servers, database servers, file servers, etc.) and are optimized for remote access, managing large volumes of data, and stability. Typical examples include Windows Server, server-oriented Linux distributions, and Unix variants.
Finally, there are embedded operating systems , found in routers, smart TVs, industrial machinery, household appliances, alarm systems, and control panels, among other devices. They are programmed to perform a very specific set of functions with limited resources and are often based on stripped-down versions of Linux or other lightweight kernels.
Based on the number of users and tasks
From the perspective of who uses them and how, a distinction is usually made between single-user and multi-user systems . A single-user system only allows one user to run programs at a time, while a multi-user system simultaneously manages the sessions and processes of several people, protecting each user's data.
Regarding task management, we talk about single-tasking and multitasking systems . A single-tasking system only executes one user process at a time (in addition to the operating system's own internal processes). Multitasking systems, on the other hand, are capable of executing several processes seemingly concurrently, alternating the CPU between them. In hardware with multiple cores or processors, this multitasking can be complemented by true multiprocessing.
A distinction is also made between single-session and multi-session systems . Many modern systems allow multiple simultaneous sessions, whether through remote desktops, SSH connections, or virtual consoles, which is very common on servers and in Linux distributions.
According to resource management and architecture
If we look at the realm of physical resources, we distinguish between centralized and distributed systems . In a centralized system, all resources (CPU, memory, storage, peripherals) belong to a single machine. In a distributed operating system, on the other hand, the resources of several computers are pooled to offer a unified platform with high computing and storage capacity , allowing remote access to files and applications as if they were local.
There are also batch operating systems , inherited from classical computing, in which the user does not interact directly during execution: jobs are grouped into batches and an operator prepares them for the system to process without continuous human intervention. They are mainly used in business environments for high-volume, repetitive tasks, such as payroll calculation or bank statement generation.
Time-sharing or interactive multitasking operating systems allow multiple users or applications to share the CPU, allocating small "pieces" of processor time to each. Unix is ​​a classic example of this approach.
On the other hand, we find real-time operating systems , designed for environments where response time must be extremely short and predictable. These are used in industrial robots, air traffic control systems, advanced medical equipment, and scientific experiments, where any delay can be critical.
A particular case is network operating systems , which run on servers dedicated to managing users, permissions, shared resources, security, and communications within a local or corporate network. Unix and NetWare are representative examples in this area.
Main functions of an operating system
The functions of an operating system are numerous and complex, but they can be grouped into several blocks that help to understand what it does every time you turn on your Windows, Linux, macOS or Android.
Process and CPU management
One of its most critical tasks is process management . A process is simply a running program that requires CPU, memory, access to files, and I/O devices. The operating system is responsible for creating and destroying processes, suspending and resuming them, and providing communication and synchronization mechanisms between them.
To achieve this, it uses various scheduling algorithms that determine which process uses the CPU at any given time , in what order, and with what priority. This allows, for example, you to listen to music while browsing the internet and an update downloads in the background, without either task completely blocking the others.
Processes can be foreground processes, when they require direct user intervention (a browser, a text editor, a game, etc.), or background processes, when they run without visible interaction (an antivirus program scanning the system, a backup service, a network daemon in Unix, etc.). The operating system must coordinate all of them to keep the machine stable and responsive.
Memory management
Another key function of the operating system is the efficient management of RAM . Every program needs memory space to store instructions and temporary data. The OS is responsible for reserving this space, protecting it from other processes, and releasing it when the application no longer needs it.
In addition to allocating and freeing memory, many systems implement techniques such as virtual memory , which allow simulating that there is more memory than is actually available by using the disk as an extension, or paging and segmentation mechanisms to organize and protect the different memory areas of processes and the kernel.
Input/output device management
The operating system also controls all data input and output through peripherals . To do this, it relies on specific drivers, developed by the device manufacturer or the community, which allow keyboards, mice, printers, external hard drives, cameras, and network cards to communicate correctly with the system.
Instead of each program needing to know the details of how a device works, the operating system provides a uniform interface for reading, writing, and configuring peripherals . This simplifies application development and makes it easier to swap devices without having to rewrite software.
File system and information management
The operating system manages the files and directories stored on disks and other media . It offers basic operations such as creating, opening, reading, writing, moving, copying, and deleting files, as well as organizing information into user-friendly folder structures.
It also maintains information critical to its own operation, such as process tables, open file tables, and system configuration data. A significant part of its job is to ensure that data is stored in order and preserved correctly , even in the event of failures or power outages.
In this area, different file systems come into play (FAT, FAT32, NTFS, ext3, ext4, XFS and many others), each with its own advantages in terms of performance, security, maximum file size or compatibility.
Security, permissions, and user control
Security is another fundamental pillar. The operating system must distinguish between authorized and unauthorized use of resources . To do this, it implements authentication mechanisms (users and passwords, biometrics, certificates), authorization (permissions on files, devices, and operations), and auditing.
Multi-user systems, such as those based on Unix or Windows server editions, are particularly demanding in this regard, as they must ensure that one user cannot access or modify another's data without permission . The system is also responsible for enforcing security policies, encrypting sensitive information, and managing updates that patch vulnerabilities.
Network and communications management
For a computer to communicate with other devices or the internet, the operating system must manage network protocols and communication interfaces . It configures IP addresses, manages wired and wireless connections, organizes access to shared resources, and maintains the communication points that applications use to send and receive data.
In this context, network operating systems and server environments play a key role, as they centralize the management of users, groups, permissions, directory services, and shared resources within an organization or private network.
System startup, monitoring, and performance
From the moment you press the power button, the operating system begins the device boot process . After the initial firmware checks (BIOS or UEFI), the OS kernel loads, essential drivers are initialized, and basic services are started so the user can log in and begin working.
During normal use, the operating system continuously monitors the computer's status: temperature, processor load, memory usage, disk space, device failures, etc. Thanks to this monitoring, it can detect errors, warn of problems, and suggest corrective actions , such as installing an update, closing unresponsive applications, or recommending a backup.
Many modern systems also include specific tools to measure and optimize performance , identify bottlenecks, defragment mechanical disks, clean temporary files, or adjust visual effects to keep the device running smoothly over time.
Backups, recovery, and virtual machines
Another important task is managing backups and data recovery . Although third-party applications are often involved, the operating system provides services and APIs for scheduling backups, taking system images, and restoring configurations or files in case of failure.
Furthermore, many systems natively support running virtual machines or containers, allowing multiple operating systems or isolated environments to coexist on the same machine. This is very useful for testing, software development, training, or running legacy applications that require older operating system versions.
Examples and features of the main operating systems
To put all of the above into perspective, it is worth reviewing the most well-known operating systems and their most prominent features , both on desktop and mobile devices.
Microsoft Windows
Windows is the most widely used desktop operating system in the world. It originated in 1985 as a graphical environment built on top of MS-DOS and eventually evolved into a complete operating system with a window-based interface, taskbar, and desktop . Its popularity is largely due to its ease of use, broad hardware and software compatibility, and the fact that it comes pre-installed on most personal computers.
With each new version (from Windows 1.0, 2.0, and 3.x to milestones like Windows 95, XP, 7, 10, and 11), Windows incorporated improvements in security, stability, graphical interface, and support for new technologies . Today, it offers features such as Secure Boot, BitLocker encryption, biometric authentication with Windows Hello, integration with cloud services like OneDrive, and a strong focus on productivity with tools like Snap Layouts and integration with Microsoft 365.
Windows 11, the latest version, also adds a redesigned interface, improved gaming compatibility thanks to DirectX and technologies like Auto HDR and DirectStorage, as well as integrated artificial intelligence features through assistants like Windows Copilot . All of this keeps Windows at the forefront for home users, businesses, and gamers.
Linux and GNU/Linux-based distributions
Linux, strictly speaking, is the kernel of an open-source operating system , around which numerous distributions such as Ubuntu, Fedora, Debian, and many more are built. The combination of the Linux kernel and tools from the GNU project results in what we commonly call "Linux distributions."
Its defining characteristic is its availability under free licenses that allow the use, study, modification, and redistribution of the software . This has led to a huge developer community and an enormous variety of distributions adapted to all kinds of needs: general-purpose desktops, servers, embedded devices, educational equipment, and security environments.
Linux is renowned for its stability and security, especially on servers and supercomputers, where it clearly dominates. Furthermore, it offers extensive customization options , allowing users to modify virtually any aspect of the interface and the system.
MacOS
macOS is the operating system developed by Apple for its Mac computers. Based on Unix technologies, it stands out for its meticulous design, its integration with Apple hardware, and its focus on user experience . The combination of system and hardware controlled by the same manufacturer allows for a high degree of optimization.
Among its strengths are integrated tools for video, image, and music editing , cross-device continuity (iPhone, iPad, Apple Watch, etc.), and a robust security model with app verification, sandboxing, and permission control. The Mac App Store also provides easy access to curated and reviewed software.
Android and iOS in the mobile field
In mobile phones and tablets, the main players are Android and iOS . Android, initially developed by Android Inc. and later acquired by Google, is based on the Linux kernel and has become the most widespread system in smartphones and tablets thanks to its openness to multiple manufacturers.
iOS (and its variant iPadOS) is Apple's mobile operating system, found on iPhones and iPads. It is notable for its deep integration with the Apple ecosystem, its security, and its strict control over applications distributed through the App Store.
Both systems, with their own particularities, fulfill the same fundamental functions as a desktop operating system, although adapted to touch screens, sensors, constant connectivity and advanced battery management.
Having considered all these elements, it becomes much clearer that the operating system is more than just "what you see on the screen": it is the piece of software that coordinates, protects, and enables the joint work of all parts of a device , whether we are talking about a Windows PC, a Linux server, a Mac, an Android phone, or a smart TV.
