Comment by adrian_b

No, modern CPUs are not at all C machines, they are about as far of C machines as one could imagine, because they now implement in hardware hundreds of instructions that were unheard of in a DEC PDP-11.

The C language has only 2 kinds of integer data types, signed and unsigned, of various sizes. Moreover, the implicit conversions between them are erroneously defined and lead to data corruption, unless the programmer is extremely careful.

Modern CPUs, like those implementing the Intel/AMD x86-64 ISA or the Arm Aarch64 ISA, have 8 different kinds of integer data types, all of various sizes. For all these different data types the CPUs have dedicated instructions that implement in hardware various operations with them.

It is impossible to access in the right way from C all these data types. Only in C++ one can define custom data types and implement appropriate operations for them using inline assembly or separate assembly source files.

Those 8 data types are signed integers where overflow causes an exception, signed integers where overflow causes saturation, non-negative integers where overflow causes an exception, non-negative integers where overflow causes saturation, integer residues a.k.a. modular integers, bit strings, binary polynomials and binary polynomial residues (i.e. elements of a Galois field).

Unfortunately, most programming languages have not gone beyond the level of C, so they do not allow the efficient use of modern CPUs otherwise than by using inline assembly or compiler intrinsics.

Thus there is a great mismatch between most high-level programming languages and modern CPUs, the opposite of what the poster above said.

The mainstream CPUs have become very similar between themselves, but very different from the C machine model inherited by most modern programming languages.