"I have worked extensively in the past with C and have never heard it referred to as a virtual machine, thin or otherwise."
True. Usually other terms are used; for instance, "memory model". If you google that you'll find some things. As you read them, notice that they may or may not match the hardware you are actually running on, and given the simplicity of C's model, nowadays almost never does.
C is a low-level language that lets you close to the machine, and even lets you drop into assembler, but it is true that it is enforcing/providing a certain set of constraints on how the library and code will act that do not necessarily match the underlying machine. It may not be a "virtual machine", depending on exactly how you define that term, but the idea isn't that far off.
Also, this is a good thing, not a criticism. If it really was just a "high level assembler" that provided no guarantees about the system, it would be as portable as assembler, which is to say, not at all.
For a much more clear example of this sort of thing in a language similarly thought to be "close to the metal", look at C++'s much more thorough specification of its memory and concurrency model, and again notice that this model is expected to be provided everywhere you can use a C++ compiler, regardless of the underlying hardware or OS. It is, in its own way, a virtual machine specification.
True. Usually other terms are used; for instance, "memory model". If you google that you'll find some things. As you read them, notice that they may or may not match the hardware you are actually running on, and given the simplicity of C's model, nowadays almost never does.
C is a low-level language that lets you close to the machine, and even lets you drop into assembler, but it is true that it is enforcing/providing a certain set of constraints on how the library and code will act that do not necessarily match the underlying machine. It may not be a "virtual machine", depending on exactly how you define that term, but the idea isn't that far off.
Also, this is a good thing, not a criticism. If it really was just a "high level assembler" that provided no guarantees about the system, it would be as portable as assembler, which is to say, not at all.
For a much more clear example of this sort of thing in a language similarly thought to be "close to the metal", look at C++'s much more thorough specification of its memory and concurrency model, and again notice that this model is expected to be provided everywhere you can use a C++ compiler, regardless of the underlying hardware or OS. It is, in its own way, a virtual machine specification.