What Is a Computer?
From Power Button to Operating System
A program cannot start itself. That is the puzzle the last lesson ended on, and it is a real one: when the machine is off, everything on the drive is inert, and inert data cannot decide to load.
Something has to go first. That something is
A chain of handoffs
Starting a computer involves a series of handoffs. Each stage prepares what the next stage needs:
Power arrives, and the CPU begins from a fixed starting point built into the
. The firmware wakes up enough of the machine to continue, and checks that the essential parts respond.
The firmware starts a
from whichever drive it has been told to use. The bootloader finds the
and loads it into RAM. That is the large program that runs everything else: Windows, , or . The operating system takes over, starts what it needs, and eventually shows you a login screen or a desktop.
The useful distinction is each stage’s job: firmware prepares the hardware, a bootloader starts the operating system, and the operating system manages the running computer. Their sizes are not what determines the order.
It is also why startup takes time. Several dependent checks and loads have to finish in order before the operating system can take over.
Deep dive
You will meet some names for these parts, mostly when reading older instructions.
The firmware standard on most current machines is
Those names do not change the sequence above. They are labels for the startup stage, and you can carry on without memorizing them.
The firmware has woken the hardware and picked a drive. What happens next?
One place we are not going
Firmware settings control which drive to start from, security features, cooling, and other hardware behavior. This course will never ask you to open them.
That is a deliberate boundary rather than squeamishness. The key that opens the settings screen differs by machine, the screens look like nothing else you use, and one changed setting can leave a computer that will not start at all. You can understand the whole startup path without going in there, and understanding it is the part that helps.
What you can explain now
Six lessons ago a computer was a box that did things. You can now say what is inside it, what each part is for, and what happens in the seconds between pressing the power button and seeing your desktop.
A document disappeared after a power cut, but the last saved version still opens and the computer starts normally. What best explains it?
Monty after this chapter
You have had Monty free throughout this chapter. From the next chapter on, its hints, alternative explanations, and error translations are part of Guided.
Before you move on, use it for the thing it is best at. Try:
Ask me questions to check whether I really understand the startup sequence, one at a time, and tell me where my answers are shaky.
Being questioned by something that can follow up on your particular wrong answer is a different experience from a fixed quiz, and it is a fairer test of whether Guided is worth it to you than anything we could write here.
All of that moved instructions and data around without once asking what instructions and data actually are. That is the next chapter.