Explain how a modern computer works at the most basic level.

Question

How do you go from some silicon wafer with some metallic lines printed on it to having a GUI desktop. I don’t understand the intersection between hardware and software at the fundamental level.

In: Technology

Answer 1

The silicon wafer with some metallic lines printed on it allows you to have logic gates with electricity. Stuff like AND, OR, XOR gates, if you have two wires in, and whatever happens to them, when they are both powered and only then, the output is powered, you have an AND gate for instance.

Now you can have arithmetic, where you will take for instance 32 wire running on parallel to define 32 bits which you (as a human) can decide represents a number between 0 and 4 million, or +-2millions (you can represent 2^32 unique values with those wires). You can use logic gates to build all the operations you want on these numbers

You can also use this principle to have memory: each bit of memory can be set and retrieved, and you can address your memory using arithmetic: give the memory unit a number (32 bits on the example below, and it will return the value of that one bit of memory.
But storing and addressing one bit at a time is tedious, so instead, you can build a memory where you will store 32bits at once, and address them as a whole. Now when provided with a 32 bit address, the memory can give you 32bits of memory back.

Now you can store and you can compute. The next thing would be to add more functionality to your core arithmetic, to build in all the functions you need, but basically, you only need a few, read memory, write memory, a loop and a conditional test.

Now how do you get another display?
Your screen is a matrix of pixels, and a pixel is basically 3 lamps (red green and blue) each lamp can be more or less bright. Let say each has 256 possible luminosity level, which are then controlled by 8 bits. A pixel is a 3 lamps so 32 bits, which can be updated by reading a number from our memory. Your monitor and gpu is doing just that, the gpu output its memory to the screen, which display what has been instructed.