Microsoft has never been shy about being acquisitive, and today it announced it’s buying Express Logic, a San Diego company that has developed a real-time operating system (RTOS) aimed at controlling the growing number of IoT devices in the world.

The companies did not share the purchase price.

Express Logic is not some wide-eyed, pie-in-the-sky startup. It has been around for 23 years, building (in its own words) “industrial-grade RTOS and middleware software solutions for embedded and IoT developers.” The company boasts some 6.2 billion (yes, billion) devices running its systems. That number did not escape Sam George, director of Azure IoT at Microsoft, but as he wrote in a blog post announcing the deal, there is a reason for this popularity.

“This widespread popularity is driven by demand for technology to support resource constrained environments, especially those that require safety and security,” George wrote.

Holger Mueller, an analyst with Constellation Research, says that market share also gives Microsoft instant platform credibility. “This is a key acquisition for Microsoft: on the strategy side Microsoft is showing it is serious with investing heavily into IoT, and on the product side it’s a key step to get into the operating system code of the popular RTOS,” Mueller told TechCrunch.

The beauty of Express Logic’s approach is that it can work in low-power and low-resource environments and offers a proven solution for a range or products. “Manufacturers building products across a range of categories — from low-capacity sensors like lightbulbs and temperature gauges to air conditioners, medical devices and network appliances — leverage the size, safety and security benefits of Express Logic solutions to achieve faster time to market,” George wrote.

Writing in a blog post to his customers announcing the deal, Express Logic CEO William E. Lamie, expressed optimism that the company can grow even further as part of the Microsoft family. “Effective immediately, our ThreadX RTOS and supporting software technology, as well as our talented engineering staff join Microsoft. This complements Microsoft’s existing premier security offering in the microcontroller space,” he wrote.

Microsoft is getting an established company with a proven product that can help it scale its Azure IoT business. The acquisition is part of a $5 billion investment in IoT the company announced last April that includes a number of Azure pieces, such as Azure Sphere, Azure Digital Twins, Azure IoT Edge, Azure Maps and Azure IoT Central.

“With this acquisition, we will unlock access to billions of new connected endpoints, grow the number of devices that can seamlessly connect to Azure and enable new intelligent capabilities. Express Logic’s ThreadX RTOS joins Microsoft’s growing support for IoT devices and is complementary with Azure Sphere, our premier security offering in the microcontroller space,” George wrote.