The core of the computer (or microcontroller)
is the central processing unit, CPU.
This is where the real magic happens.
The states (bits) of all input, output and control lines
are held here in extra flip-flops, called registers.
The pivotal register is the program pointer.
When you turn on the computer, it starts with
the value "0" and is increased by 1
on every tick of a clock.
This clock is a quartz crystal oscillator,
just like in a wrist watch, only much faster.
A 16 MHz clock ticks 16 million times each second,
a 2 GHz clock 2 billion times each second,
to give two examples (microcontroller vs PC).
A quartz crystal in an electric circuit resonates
with a very reliable frequency that is used to
trigger reading and writing cycles in the CPU,
including increasing the program pointer.
The program pointer is an address for the
program memory, so as it starts with 0,
the program memory data at address 0
is the first "line of code" executed.
On the next tick of the computer clock,
the program pointer becomes 1, and the
second "line of code" gets executed, and so on.
Learning Programming with Eas — the Tutorial by Molaskes
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