00:00Have you ever really stopped to think about the device you're using right this second?
00:04I mean, it's basically a box of refined sand, metal, and plastic.
00:08And yet, it connects you to the entire world,
00:11runs unbelievably complex software,
00:14and seems to understand your every command.
00:16It feels like magic, doesn't it?
00:18Well, today we're going to pull back the curtain on this everyday magic.
00:21So let's just dive right in with the big central question.
00:25How on earth does this inanimate object follow our instructions?
00:29How does it actually work?
00:31To get to the bottom of that,
00:32we're going to build our understanding from the ground up, piece by piece.
00:36We'll start with what a computer even is,
00:38peek inside its brain, learn its language,
00:41check out its memory system, see how it thinks,
00:43and then zoom out to see how all this leads to the supercomputers that are shaping our world.
00:48Okay, let's get into it.
00:50Before we can understand how a computer works,
00:52we need to agree on what it actually is.
00:54I know, it sounds basic, but its core identity is really important.
00:58The absolute keyword here is programmable.
01:01Think about it.
01:02A simple calculator is built to do one thing, math.
01:05But a computer, you can give it a totally new set of instructions,
01:08a new program, and it can solve a completely different problem.
01:11That's the game changer right there.
01:12So, if a computer's main job is to run all these different programs,
01:17what's the part that's actually doing all the heavy lifting?
01:20Let's take a look inside the engine room.
01:23Meet the central processing unit, the CPU.
01:26This thing is the absolute heart of the machine.
01:28You can think of it as the command center,
01:30where all the important action happens.
01:32And it's really made of two crucial parts that work together.
01:36Okay, so this is where the raw number crunching goes down.
01:40The arithmetic logic unit, or ALU.
01:43This is the mathematician in the duo.
01:45It's doing all the adding, subtracting, you know, the math.
01:48But it also handles logic, which is just as important.
01:52It answers questions like, is 64 greater than 65?
01:56So, if the ALU is the mathematician,
01:58the control unit is the director of the whole show.
02:01It doesn't do any of the math itself.
02:03Nope.
02:04Instead, it reads the program's instructions
02:06and just tells everyone else what to do.
02:08It tells the ALU what numbers to crunch
02:10and tells the memory where to get the data
02:12and where to put the answers.
02:13It's the ultimate orchestra conductor.
02:16Right.
02:16So, we've got a director and a mathematician in the CPU.
02:20But, what language are they speaking?
02:22You might be shocked at how incredibly simple it is.
02:25The entire, and I mean entire, vocabulary of a computer
02:29starts right here, with a zero.
02:32You can think of it as off.
02:34And this, this is the only other word it knows.
02:38A one, which means on.
02:41Seriously, that's the whole thing.
02:43Now, let that sink in for a second.
02:44Every single photo you've ever seen,
02:47every song you've listened to,
02:48every app on your phone.
02:50At the most fundamental level,
02:51it's all just a ridiculously long and complicated sequence
02:54of these ones and zeros.
02:55Each one of these digits is called a bit.
02:58And inside your computer's CPU,
03:00there are literally billions of microscopic transistors
03:02that act like tiny little light switches.
03:05Each one can either be off, representing a zero,
03:08or on, representing a one.
03:10That's the physical reality
03:11behind the computer's super simple language.
03:15Okay, so the CPU is juggling billions of these bits
03:17all the time.
03:18But where does it keep them
03:20while it's in the middle of a task?
03:21It needs a workbench, a workspace.
03:23We just call it memory.
03:25The main workspace is called random access memory, or RAM.
03:29Think of it as the computer's short-term memory.
03:31It's incredibly fast and holds all the data
03:34for the programs you have open right now.
03:36The catch?
03:36It's volatile,
03:37which means when you turn the power off,
03:39poof, everything in it is gone.
03:41But here's the thing.
03:43Memory isn't just one big bucket.
03:44It's a hierarchy, a pyramid.
03:46The fastest, most exclusive memory,
03:49called registers,
03:50is actually inside the CPU,
03:52but there's hardly any of it.
03:54Then you have cache,
03:55a little bit slower,
03:56but still on the CPU chip.
03:57Then you have RAM on the motherboard,
03:59and way down at the bottom,
04:00your big, slow storage drive.
04:02The computer is constantly,
04:04cleverly moving data between these levels
04:06to give you the best of both worlds,
04:07speed and size.
04:09All right, we've got the brain,
04:11we've got the language,
04:12and we've got the workspace.
04:14Now we can finally put all these pieces together
04:16and see how a computer
04:17actually follows a list of instructions,
04:19how it thinks.
04:21I really love this analogy.
04:23A computer running a program
04:24is a lot like us reading a book.
04:27Most of the time,
04:27it just goes line by line,
04:29step by step.
04:30But sometimes,
04:31it gets an instruction to jump back
04:33and re-read a chapter,
04:35or to skip ahead a few pages
04:36if a certain condition is met.
04:38This ability to loop and make decisions
04:40is what makes computers
04:42so incredibly powerful.
04:43And this is what those instructions
04:45actually look like,
04:46way down at a low level.
04:48This is a language called assembly.
04:50Because the CPU can only do
04:51really simple things,
04:53we have to break down a big task,
04:54like say,
04:55adding up all the numbers
04:56from one to a thousand
04:57into these tiny little baby steps.
04:59You can literally see the commands here,
05:01add, compare,
05:02and then that crucial command
05:04to loop back and do it all again.
05:06So to run that code,
05:08the CPU does this simple four-step dance
05:10over and over and over.
05:12It fetches an instruction,
05:13the control unit decodes it,
05:15the ALU executes it,
05:17and the result gets stored.
05:18Fetch, decode, execute, store.
05:21That's the heartbeat of the computer.
05:22And a modern CPU does this
05:24billions of times,
05:26every single second.
05:27It's just wild.
05:28Okay, let's zoom all the way out.
05:31We've seen the fundamental pieces,
05:32a simple on-off switch,
05:34and a basic four-step cycle.
05:36How do we go from that
05:37to the mind-boggling power
05:39of modern computers?
05:40Well, it's a story
05:41all about getting smaller.
05:43Those on-off switches started out
05:44as big, hot,
05:46unreliable vacuum tubes.
05:47Then came the much smaller,
05:49more reliable transistors.
05:50Then we figured out
05:51how to cram thousands of those
05:53onto a tiny integrated circuit,
05:55which led directly
05:56to the very first microprocessor
05:57back in 1971.
05:59The basic logic never changed,
06:01just the scale.
06:02And it changed dramatically.
06:05Get this,
06:06that first microprocessor
06:07from 71
06:08had about 2,300 transistors.
06:10The chip in the phone
06:11in your pocket right now,
06:12it has over 15 billion.
06:15That incredible density
06:16is why your smartphone
06:17has way more computing power
06:18than all of NASA had
06:19when they put a man on the moon.
06:21And today's supercomputers,
06:22they link together
06:23thousands of these modern chips
06:24to tackle problems
06:25we once thought were impossible,
06:26like forecasting weather
06:28across the globe
06:28or simulating new medicines.
06:30So from a simple on-off switch,
06:33literally made from sand,
06:34performing a simple four-step cycle,
06:36we've built machines
06:37that can simulate
06:38the entire universe.
06:39It's an absolutely astonishing
06:41journey of scale.
06:42And it leaves us
06:43with one last huge question
06:44to think about.
06:45If these simple,
06:46simple rules
06:47can create this much complexity,
06:49what comes next?
06:50Are there any limits at all?
Comments