 <p>Your best bet will be to learn Objective-C. It's not difficult to pick up, especially if you already have a strong understanding of C. (It's a much smaller and simpler extension of C than C++, for instance.)</p> <p>Your options other than that are quite limited:</p> <ul> <li><p>There's Carbon, Apple's legacy C framework for UI development. <strong>Using it is not recommended</strong>. Carbon was never updated to support 64-bit applications, and lacks many features that have been added to Cocoa since the 64-bit transition (~2005). It's also very awkward to write an application in, as it was designed in large part to ease porting of applications written for Classic Mac OS.</p></li> <li><p>There's also X11, with an appropriate UI library like GTK. <strong>I wouldn't recommend this either</strong>. Neither X11 nor any UI libraries for it are installed by default -- they must be installed by the user -- and applications which use X11 have a significantly different interface from native applications.</p></li> <li><p>A third-party UI library. Most of the ones I can think of offhand (QT, wxWidgets, and FLTK) require C++, though. <a href="https://www.gtk.org/download/macos.php" rel="nofollow noreferrer">GTK+</a> does have a C interface and natively supports a macOS interface, but it's not particularly native.</p></li> <li><p>A library specific to your use case. Impossible to recommend one without knowing more about what you're trying to do.</p></li> <li><p>Nothing. That's right, nothing at all. If you just need to let the user view an image, you can save it to a file and use the <code>open</code> command-line tool to open it in the Preview application. It's janky, but it's also really easy.</p></li> </ul>