Linux is an example of:

Linux is categorized as open-source software, which means that its source code is available for anyone to view, modify, and distribute. This model promotes community collaboration and innovation, allowing developers and users to contribute to the software's development and evolution. The open-source nature of Linux fosters a diverse ecosystem of distributions and applications that cater to a wide range of users, from individuals to businesses.

In contrast, the other options focus on different aspects of software. For instance, software that's primarily concerned with end-user tasks may include operating systems or applications like word processors, which aren't limited to the collaborative and modification aspects of open-source software. Software designed for specific machines refers to proprietary or closed systems tailored for particular hardware, which does not align with the open-access principles of Linux. Lastly, while Linux can be useful for numeric data processing within certain applications, this does not capture the essence of its identity as open-source software, which is a broader characteristic encompassing various functionalities beyond just numerical processing.