One of the great advantages of a digital computer, when used in the application of instrumentation and control (I & C), is the ability to replace routine software (programming) for hardware logic. This becomes very interesting if the software logic can be done in time to death on the computer. Many computers will Loaf with doing little or nothing most of the time. With skillful manipulation of interrupts and the right programming, I can often adjust computer to perform logical operations that should be a hardware problem.
Software approach is also sometimes more efficient than hardware.I can change the program at will by reprogramming the memory (ROM) chip is read-only. To make major changes in hardware requires a bit more effort, including the possibility of redesigning the printed circuit board (PCB) and the chassis wiring scheme. I also get the flexibility to have "universal machine" of a computer.
I could make a standard single-board computer or a universal system board mating with a common motherboard that will be used in a variety of different projects. Some companies make single-board computer based on the popular microprocessors. This board has some limited RAM and usually around 2K bytes of ROM on board.
By using the data, address, and the I/O buses, the designer can press into service the same board in a dozen different applications. The same computer board, loaded with different programs in ROM, will perform different functions.
"Microcomputer Interfacing Handbook: A/D & D/A" by Joseph J.Carr, first edition 1980, chapter 16th
