To understand a subject, certain requirements must be fulfilled.
I must understand vocabulary and language - the human concepts that map to my existing knowledge.
I can't say I understand coffee and espresso, and then be lost when you mention 'crema'. The crema is the tan-colored mixture of oils and air-bubbles that float to the top of an espresso shot. The consistency of the crema says a lot about the underlying chemistry of the bean, the oil content and the extraction process. The more I understand subtle elements, the more deeply I understand the ingredients and processes involved in the making of espresso.
The same is true with other topics of human knowledge.
I write about the underlying concepts in order to discover where there might be gaps in my understanding.
Computer code is run with a command. How did the original person write code to send the start and stop commands?
Before start and stop commands, the only way to stop the computer would have been to turn off the electricity. Then, somebody had the idea of putting a nozzle on the hose so they could have the water flowing, but controlled at the nozzle. This enabled writing programs on the same machines that run the programs. Prior to this, the programs were written on cards fed into computer memory prior to program execution.
To be able to start, run and stop a program, the Loop had to be invented. The loop is a repeating process.
Check for input.
Check for input.
The input can come from a keyboard or mouse or microphone these days. These are input.
Before I get too far down the rabbit hole of computers, let's just say that everything had to be invented and the reasons for the inventions came from the needs of the moment.