HTC has detailed the circuitous 12-step process as part of their Software Update status page, which tracks the company's progress in rolling out the latest version of Android to their flagship handsets. A monstrous 10,000-pixel-tall infographic walks readers the procedure, beginning when Google notifies the carriers of what they will include in Android's next version bump.
Before the update's public announcement, Google releases a "Platform Development Kit," or PDK, to its manufacturing partners. The PDK is essentially the hardware equivalent of a software SDK --?it provides the tools necessary for device manufacturers to build Android-compatible hardware.
The update's source code is not released until after Google makes their public announcement, when it is shipped off to both handset manufacturers, like HTC, and chipset makers, such as Qualcomm, for evaluation. Both parties must agree to support the update before it can move forward, the first of several points at which the process can be derailed.
No less than four stakeholders must agree in order for an Android update to run the gauntlet and make it to customer devices.
Chipset makers that elect to move forward with the update then begin the process of creating and optimizing new drivers for their hardware. It is up to each manufacturer to decide which chipsets will be targeted -- devices using chipsets that do not make the cut, no matter their age, will be unable to run the newest Android version.
Until this point, the process is the same for all three classes of Android devices made by HTC --?carrier devices, customized for and sold by carriers like Verizon Wireless; unlocked and developer edition devices, sold directly from HTC to customers; and Google Play edition devices, which run versions of Android unadulterated with carrier or manufacturer customizations. Once the chipset makers have had their say, however, each device follows a slightly different path.
For carrier and developer devices, the handset manufacturer can begin merging the Android and chipset updates with their existing code base. In HTC's case, this means integrating their HTC Sense user interface customizations.
Carriers then become involved, dictating which special applications, services, and carrier-specific modifications will need to be made. Google Play and developer edition devices are not subject to the carriers' whims, one reason why those handsets have already received their Android 4.4 "KitKat" updates while carrier phones have been forced to wait until 2014.
After internal testing, the updates are sent out for certification by carriers, regulatory bodies, and Google itself. Any of these players can delay the update and force changes to be made, but Google maintains final approval - without Mountain View's OK, the update will never see the light of day.
Apple, in comparison, faces a single stakeholder when it comes to iOS updates: themselves. They need only regulatory approval and technical certification from carriers --?Apple famously released their cross-platform messaging service, iMessage, without consulting any of their carrier partners.
The effects of this dichotomy are illustrated by the latest version distribution statistics. Cupertino's newest operating system, iOS 7, now runs on more than three-quarters of all iOS devices, while Android 4.4 "KitKat" is found on a relatively miniscule 1.1 percent of devices, according to Google's developer dashboard.