On some machines the operation of data path between ALU and registers is controlled by microprogram . On some machines , it is controlled by hardware .On machines with software control of the data path, the microprogram is an interpreter for the instructions at machine level. It fetches, examines, and executes instructions one by one, using the data path to do so.
For example, for an ADD instruction, the instruction would be fetched, its operands located and brought into registers, the sum computed by the ALU, and finally the result routed back to the place it belongs. On a machine with hardwired control of the data path, similar steps would take place, but without an explicit stored program to control the interpretation of the machine level instructions.
I am unable to get that if there is no microprogram in the latter case then how is the hardware able to interpret instructions directly ?