Operating system

An operating system (OS) is system software that helps manage computer hardware and software. It makes sure everything works together smoothly.

Time-sharing operating systems help computers do many things at once. They keep track of how the computer’s power and space are used.

Operating systems are used on many devices, like phones, game consoles, and big servers. As of November 2025, Android is the most common operating system on smartphones. Other popular ones are Microsoft Windows for desktop computers, iOS and iPadOS for Apple devices, and macOS for Mac computers. Linux is often used on servers and very powerful computers. Some operating systems are made for special tasks, like controlling machines or protecting information.

Definition and purpose

An operating system is like a helper for your computer. It manages the computer's resources so that everyone who uses the computer and all the programs can work together smoothly. It includes special software called a kernel that is always running, plus other helpful tools.

The operating system has three main jobs:

• It shares the computer's power and memory between different programs so that no single program can take over everything. It also keeps programs safe from each other.
• It makes using the computer's hardware easier for programmers by hiding complicated details.
• It offers common services, like ways to connect to networks or save files, so programs can run on different types of computers without needing changes.

Types of operating systems

Operating systems help manage computer hardware and software. Some are made for many computers working together, like in cloud computing. They help computers share tasks and information well.

Other operating systems are made for special uses, like in home appliances or devices that need to work at exact times, such as in manufacturing. Some can run inside other systems, letting different tasks be tested or moved between computers easily.

History

Main article: History of operating systems

The earliest computers from the 1940s and 1950s needed people to set them up by hand or use special cards. When transistors were invented, bigger computers called mainframes were made. These still needed someone to manage them, but they started to have simple operating systems to help run programs.

In the 1960s, IBM made computers that all used the same operating system, OS/360. This system could handle multiple tasks at once. Around this time, ways to let many people use a computer together were developed. One system, MULTICS, aimed to let many users access a big computer. From this, the UNIX operating system grew, which led to versions like System V and BSD. A simpler version called MINIX inspired Linux, which is now used in many places.

The creation of personal computers became possible in the 1980s. For a while, CP/M was the most common operating system for small computers. Later, IBM and Microsoft created MS-DOS, which became popular. The first computer to use a graphical user interface was Apple's Macintosh. This idea was later added to MS-DOS by Microsoft, creating Windows. Today, Windows is still used on personal computers, while UNIX systems like Linux are common on business computers. On mobile devices, Symbian OS was first, followed by BlackBerry OS and iOS. Eventually, the open-source Android operating system became popular for smartphones and other mobile devices.

Components

The parts of an operating system work together to make sure all the pieces of a computer work well together. All programs need the operating system to talk to the computer's hardware.

Kernel

The kernel is an important part of the operating system. It keeps different programs and users separate to make the computer more reliable and secure. It helps keep errors in one program from affecting others and stops any one program from taking over the whole computer.

Program execution

The operating system helps programs talk to the computer's hardware. When a program starts, the operating system sets up space for it to work and gives it what it needs to run.

Interrupts

Interrupts are signals that tell the computer to stop what it's doing and handle something else right away. This helps the computer respond quickly to things like pressing a key or moving a mouse. There are two types of interrupts: ones that come from the computer's hardware and ones that come from programs.

Input/output

The operating system includes special programs called drivers that help the computer talk to devices like keyboards, mice, and hard drives. When you press a key or move a mouse, the computer uses interrupts to respond right away.

Memory management

The operating system keeps track of all the memory in the computer to make sure each program gets the space it needs and doesn't interfere with others.

Concurrency

Modern operating systems can handle many tasks at once. They use threads, which are smaller parts of programs that can run separately.

File system

The operating system helps you store and organize files on the computer. It uses filenames and folders to keep track of where things are. It also makes sure your files are safe even if the computer turns off suddenly.

Networking

Most operating systems include ways to connect to other computers and the internet.

Security

Operating systems protect your computer from things that might try to hurt it. They keep your information safe and make sure only the right people can see or change it.

User interface

Operating systems have ways for you to talk to the computer. You can either type commands or use a graphical interface with windows, icons, and a mouse. Most people prefer the graphical way because it's easier to use.

Operating system development as a hobby

Main article: Hobbyist operating system

Some people like to create their own operating systems for fun. They build these systems from the beginning, not by copying others, and they usually have just a few users and developers.

People can make these systems for simple devices, like a small computer board using a 6502 microprocessor, or for regular computers. They might use new ideas or copy parts of existing systems. The person making the system works alone or with a few friends who share the same interest.

Examples of such hobby operating systems are Syllable and TempleOS.

Diversity of operating systems and portability

When an application is made to work on one kind of operating system and then changed to work on another, it might need some changes. Each operating system works a little differently, which can take time and effort.

To avoid this problem, some applications are built using special tools like Java or Qt. These tools help the application work on many different operating systems with fewer changes. Another way to make things easier is for operating system makers to follow common rules, such as POSIX, which helps applications run better on different systems.

Popular operating systems

Further information: Usage share of operating systems and Comparison of operating systems

As of October 2025, Android is the most popular operating system, followed by Microsoft Windows, iOS, iPadOS, macOS, and Linux. Android, iOS, and iPadOS are for mobile devices, while Windows, macOS, and Linux are for desktop computers.

Linux

Main article: Linux

Linux is free software that anyone can use and change. It can run on many different kinds of computers. Linux has a graphical user interface you can use with a mouse, or you can type commands to tell the computer what to do.

Android is an operating system based on Linux that is used on many smartphones and other devices like smart watches, automotive dashboards, and home appliances.

Microsoft Windows

Main article: Microsoft Windows

Windows is an operating system used on many types of computers and devices, including desktop computers, laptops, tablets, and Xbox consoles. It was designed to be secure and reliable. Windows includes features to help protect your information and manage how programs run on your computer.