Computer programs are sequential. They are performed in the order they are presented. There are control commands to change the sequence of computer programs. Hal algebra has no sequence control because there is no sequence. All the codes of Hal algebra operate at the same time, all the time.
Fetch works on the memory, which has been stuffed with programs and data.
It makes little data streams from the code and data and sends them to decode. Decode is a primitive motor doing if-then logic. The world now runs on this stupid hardware.