Since data and instructions are stored in RAM in pretty much the same way, a priori the CPU cannot distinguish each other, but by the cycle in which the binary chunk is fetched from memory. In the case of instructions, it then needs to decode the operation codes into instructions, with the added problem that if the operation is performed on data that is not implied by the operation code, the results are wrong or even catastrophic.

The question is: would it be useful if in hardware, each cell of data would carry its own type designation? I will discuss here the pros and cons of this approach, in respect to hardware and software architectures. Continue reading →