It seems that this APL (Address Programming Language) notation is kind of a high-level microcode, similar to one used in Intel x86 CPUs, assuming that not only RAM words, but every register and I/O port are also directly addressable.

Of-course microcode is executable, but Address notation was manually translated into each specific CPU architecture.

Since every operation defined as a set, it seems it supported expressing SIMD-style vectorized computations.