It's eight years since we first heard rumors of Microsoft's Courier, a kind of dual-screen tablet that folded in half like a book, designed for note-taking and sketching and similar tasks. Courier was never officially acknowledged, but in 2010 word got out that it was cancelled.

But as patent applications show, Microsoft is continuing to work on the dual screen, folding concept. In January, a trifold design with a flexible screen and multiple hinges was patented. Over the last week, yet more new patents have been published, again showing devices with either multiple or folding screens, and in the very latest, complex hinging mechanisms. This time, the devices pictured have a single hinge and a two-part screen, much like the Courier concept.

At the same time, rumors continue to swirl that Microsoft is working on a hardware product codenamed "Andromeda" that will be some kind of a folding, portable device, released in either 2018 or 2019. Patent applications have revealed details of Microsoft hardware before—we learned that the company was working on an all-in-one, the Surface Studio, through patents—and so taking the patents and Andromeda rumors together, it seems inevitable that the company is working on something like this.

The rumors also cover the software side of things to an extent. Microsoft is continuing to work on unifying the Windows platform. The kernel and other core components have been substantially integrated, and now the focus has been on the shell and other user interface components. Currently, each Windows variant—desktop/tablet, phone, HoloLens, and even Xbox—has its own unique user interface code. Over the last year, Windows Central has reported that, at the very least, the desktop, tablet, and phone interfaces are being unified into a single shell known as CShell.

Leaked images so far suggest that the new shell will still look and feel very similar to the current phone and desktop interfaces. The purpose of the unification isn't to change the interface, it's to open the door to versatile devices that offer a mobile interface when on the go but maintain full familiar desktop shell when at home or in the office. Windows 10 Mobile gave a taste of this concept with its "Continuum" feature, wherein a Windows 10 Mobile phone can offer a simple desktop, mouse, and keyboard environment. CShell would transform this into a full fidelity desktop environment.

Extensive development doesn't mean that Microsoft will necessarily bring the device to market. A Surface Mini tablet was developed by the company but cancelled just days before it was due to be publicly announced.

What none of the rumors and patent applications have done so far is make clear precisely what the new hardware will do to turn around Microsoft's position in the mobile market. While Windows of course has an abundance of desktop applications, any mobile form factor is liable to run into the same application gap problem as Windows Mobile and Windows Phone did before it. To overcome this, the company would need to build hardware that was compelling enough to buy in spite of a lack of applications. While these folding, hinged designs certainly show novelty and hold some technical intrigue, that's a long way short of being a viable product.

Listing image by Microsoft