Bedrock of Software – Part 4: Operating Systems Written in C

In the previous posts, we explored how C laid the groundwork for modern programming languages and shaped the software landscape. We’ve looked at C’s influence on languages and traced its role as the foundation for today’s development tools. Now, we turn our attention to another critical area where C’s impact is undeniable: operating systems.

We have already talked about the relationship between C and Unix here. However, the relationship with C and operating systems are not limited to Unix. Unexceptionally, all operating systems we use today (Windows, Linux, Mac OS, IOS, Android etc.) are either primarily or entirely written in C. So C is has a monopoly on writing operating systems. Of course, it is not an accident. C became the language for operating system development because it offered the right mix of control and flexibility. It provides programmers low-level access to hardware while providing high-level abstractions that made writing complex software manageable. This balance allowed C to be both powerful and efficient.

UNIX

UNIX was a groundbreaking invention in the foundation for modern computing. Originally developed in assembly language, UNIX was rewritten in C, which allowed it to become portable across different hardware. This move made UNIX one of the first truly adaptable operating systems, as it could be recompiled on various machines without needing significant changes. By using C, UNIX established a model of simplicity and efficiency that would influence system design for decades to come.

In the second part of this series, we explored the symbiotic relationship between UNIX and C. The development of C was driven by the needs of UNIX, while UNIX’s portability spread C’s influence. As a result, C became the language for future operating systems. It also inspires the design of later systems like Linux, Windows, and macOS. UNIX’s use of C set a precedent for how programming languages and operating systems could evolve together, shaping the direction of software development.

Linux

The Linux kernel (the heart of the Linux operating system) is written in C. C’s ability to provide direct access to memory and hardware-level control made it an ideal choice for kernel development. It allows developers to fine-tune system performance, manage resources, and handle low-level tasks that are critical for an operating system’s stability and speed.

C’s simplicity and flexibility played a key role in Linux’s rise. Its straightforward nature made it easier for contributors around the world to understand and modify the code. As a result, Linux became a collaborative effort, with developers from different backgrounds enhancing and expanding it. This accessibility, enabled by C, helped Linux grow into one of the most influential operating systems today.

While Linux is widely used in servers and desktop computing, its impact extends to many other devices that run custom Linux-based operating systems. For example, the Nintendo Switch gaming console uses a Linux-based operating system to manage hardware resources efficiently and deliver gaming performance. Other devices like smart TVs, routers, and even cars also run custom versions of Linux.

As we know, Linux is an open source operation system and you can find Linux kernels source code here.

Android

Android (currently the world’s most widely used mobile operating system) is built on a modified version of the Linux kernel. This provides Android with the same low-level control over hardware that makes Linux efficient especially in an environment like mobile devices which requires performance. Beyond the kernel, C plays a critical role in Android’s performance, particularly in areas where high efficiency is needed, such as gaming and multimedia processing. Android’s Native Development Kit (NDK) allows developers to write parts of their apps in C or C++, enabling more direct access to system resources and providing better performance for CPU-intensive tasks.

Windows

The development of the Windows NT kernel marked a significant shift for Microsoft. It aimed to create a modern, stable, and scalable operating system for ordinary users. Not too difficult to guess, C played an important role in building this foundation too. The decision to use C for the kernel allowed developers to handle critical system tasks with efficiency. C’s close-to-the-metal capabilities gave Windows NT the performance it needed to compete in both personal and enterprise environments, where reliability and speed were crucial.

While later versions of Windows mainly used C++ for higher-level functionalities, C still remained essential to the core. C++ is not too far from C after all. The kernel continued to rely on C for low-level tasks, such as direct hardware communication and interrupt handling. This hybrid approach ensured that Windows could offer a powerful and stable core while taking advantage of C++’s object-oriented features for building higher-level applications.

macOS / IOS

C played a key role in the development of macOS and iOS as well. They both are built on the Darwin operating system. Darwin is a Unix-based system and it relied heavily on C for its core components. This allowed Apple to create a powerful and stable foundation that could handle the performance demands of modern computing. C’s influence extends beyond the kernel. Many system-level libraries and frameworks that power macOS and iOS were also written in C or C-derived languages.

Solaris

Solaris is another operating system written in C. Many of you may not be familiar with it. It is developed by Sun Microsystems and it is just another Unix-based operating system. It is known for its scalability for enterprise environments requiring high performance and stability. After Oracle acquired Sun and it is rebranded as Oracle Solaris.

Other Embedded Operating Systems and C

C remains the dominant language in embedded systems development as well. From microcontrollers in everyday appliances to critical systems in medical devices, C allows developers to optimize performance and ensure reliability in even the most resource-constrained scenarios. In Real-Time Operating Systems (RTOS) such as those in automotive systems or industrial automation mainly rely on C’s ability to execute tasks quickly and predictably without unnecessary delays.

Conclusion

In conclusion, C’s role in operating systems development is unparalleled, having shaped the very foundation of the digital world we live in today. From UNIX to modern giants like Linux, Windows, macOS, and Android, C’s balance of power and simplicity has made it the language of choice for system-level programming. Its influence extends beyond general-purpose operating systems, powering embedded systems and real-time applications that demand precision and reliability. As technology continues to evolve, C remains a cornerstone of computing, ensuring performance and efficiency across diverse platforms and devices.

Sharing on social media: