How is machine language run? [closed]

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This question does not really relate to any programming language specifically, it relates to, I think, EVERY programming language out there.

So, the developer enters code into an IDE or something of the sort. The IDE turns that, directly or indirectly (maybe there's many steps involved: A turns it into B turns it into C turns it into D, etc.), into a machine language (which is just a bunch of numbers). How is machine language interpreted and run? I mean, doesn't code have to come down to some mechanical thing in the end, or how would it be run? If chips run the code, what runs the chips? And what runs that? And what runs that? On and on and on.

Answer 1

There is nothing really mechanical about it - the way a computer works is electrical.

This is not complete description - that would take a book. But it is the basis of how it works.

The basis of the whole thing is the diode and the transistor. A diode or transistor is made from a piece of silicon with some impurities that can be made to conduct electricity sometimes. A diode only allows electricity to flow in one direction and a transistor only allows electricitry to flow in one direction with an amount proportional to the electricity provided at the "base". So a transistor acts like a switch but it is turned on and off using electricity instead of something mechanical.

So when a computer loads a byte from memory, it does so by turning on individual wires for each bit of the address address and the memory chip turns on the wires for each data bit depending on the value stored in the location designated by those address wires.

When a computer loads bytes containing an instruction, it then decodes the instruction by turning on individual wires that control to other parts of the CPU:

If the instruction is arithmetic then one wire may determine which registers are connected to the arithmetic logic unit (ALU) while other wires determine whether the ALU adds or subtracts and another may determines whether it shifts left or does not shift left.

If the instruction is a store then the wires that get turned on are the address lines, the wire that determine which register is attached to the data lines, and the line that tells the memory to store the value.

The way these individual wires are turned on and off is via this huge collection of diodes and transistors, but to make designing circuits manageable these groups of diodes and transistors are clumped into groups that are standardized components: logic gates like AND, OR and NOT gates. These logic gates have one or two wires coming in and one coming out with a bunch of diodes and transistors inside. Here is an electrical schematic for how all the diodes and transistors can be wired up to make an OR gate: http://www.interfacebus.com/exclusive-or-gate-internal-schematic.png

Then when you have the abstraction level of logic gates it is a much more manageable job to design a CPU. Here is an example of someone who built a CPU using just a bunch of logic gate chips: http://cpuville.com

Turns out there is already a book! I just found a book (and accompanying website with videos and course materials) for how to make a computer from scratch. Have a look at this: http://nand2tetris.org/