What is referred to as the abstraction layer that allows code to run without dependence on the underlying hardware?

Compute virtualization is the correct answer because it provides a mechanism that enables applications to run independently of the physical hardware. In compute virtualization, the underlying physical resources of a server are divided into multiple virtual instances, allowing different operating systems and applications to operate in isolated environments as if they were running on their dedicated hardware. This abstraction layer facilitates greater flexibility, resource efficiency, and scalability, as it allows organizations to allocate and manage hardware resources seamlessly.

In contrast, Infrastructure as a Service (IaaS) refers to a cloud computing model offering virtualized computing resources over the internet, but it encompasses more than just the abstraction layer. Hardware abstraction pertains to the general concept of creating a simplified interface to manage complex hardware resources, but it does not specifically encapsulate the broader functionalities provided by compute virtualization. Virtual machine hosting describes the service of hosting virtual machines but does not define the abstraction aspect of the resource management, as it is more focused on the act of hosting than on the conceptual layer that separates software from hardware.