Which of the following is not a common cloud service model?

The selection of "Programming as a Service" as the answer is accurate because it does not represent an established or commonly recognized cloud service model. In cloud computing, the predominant service models include Software as a Service (SaaS), which delivers software applications over the internet; Platform as a Service (PaaS), which provides a platform allowing customers to develop, run, and manage applications without the complexity of building and maintaining the infrastructure typically associated with developing and launching apps; and Infrastructure as a Service (IaaS), which offers virtualized computing resources over the internet.

"Programming as a Service" is not a standard classification within cloud services. Although programming can occur in various cloud environments, it does not constitute a formal service model like the others listed. Thus, identifying "Programming as a Service" as the incorrect one clarifies the understanding of widely accepted cloud service frameworks.