At what point, and how, does computer hardware touch/move/influence the software?
In: Technology
For the hardware that provides input to your computer:
First, the hardware translates its activity (such as key on keyboard being pressed; or light being sensed in a sensor in a camera, etc) into electronic signals. Then, the hardware translates those electric signals into numbers, and makes those numbers available for the software to read at a specific memory location.
For hardware that accepts output from your computer, the information flows in reverse using the same path:
The hardware makes available a numbers of memory locations that the software can write to. Software can use these memory location to give hardware data, and instructions on what to do about that data. The hardware then translates those instruction and data into its activities.
Discovering what hardwares are available, and then negotiation these specific memory locations for talking to each of the available hardware, is a large part of what your computer when it boots up.
During computer operation, the hardware and software can talk either periodically, or on an as-needed basis. The specific method is also negotiated at boot up time.
If set to the periodic method (say, 25 times per second, thus once every 40 millisecond) then the hardware and software must finish writing to their memory locations before the time is up, and then read from their memory locations when the time is up.
If set to as-needed method, then the hardware must connect to a special set of signals to the computer’s CPU called “interrupts”, so that the hardware can let the software know that it “needs to talk”.
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