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  • Do you remember when you first realized

  • that your computer was more

  • than just a monitor and keyboard?

  • That between the mouse click and the video playing,

  • there was something that captured your intention,

  • understood it,

  • and made it real?

  • What is that something?

  • Is it gremlins?

  • Let's imagine that we can shrink down

  • to the size of an electron

  • and inject ourselves into a click of a mouse.

  • If you took your mouse apart,

  • you'd see that it's really a very simple machine.

  • It has a couple buttons

  • and a system for detecting motion and distance.

  • You might have an optical mouse

  • that makes these measurements with lights and sensors,

  • but older ones did this with a hard rubber ball

  • and some plastic wheels.

  • Same concept.

  • When you click the button on your mouse,

  • it sends a message to the computer

  • with information about its position.

  • When your mouse click is received,

  • it's handled by the basic input/output subsystem.

  • This subsystem acts like the eyes and ears

  • and mouth and hands of the computer.

  • Basically, it provides a way for the computer

  • to interact with its environment.

  • But it also acts like a buffer

  • to keep the CPU from being overwhelmed by distractions.

  • In this case, the I/O subsystem decides

  • that your mouse click is pretty important

  • so it generates an interrupt to the CPU.

  • "Hey, CPU! Got a click here."

  • The CPU, or central processing unit,

  • is the brains of the whole computer.

  • Just like your brain doesn't take up your whole body,

  • the CPU doesn't take up the whole computer,

  • but it runs the show all the same.

  • And the CPU's job, its whole job,

  • is fetching instructions from memory

  • and executing them.

  • So, while you're typing, typing, typing,

  • maybe really fast,

  • like 60 words a minute,

  • the CPU is fetching and executing

  • billions of instructions a second.

  • Yes, billions every second:

  • instructions to move your mouse around on the screen,

  • to run that clock widget on your desktop,

  • play your internet radio,

  • manage the files you're editing on the hard drive,

  • and much, much more.

  • Your computer's CPU is one heck of a multitasker!

  • "But oh my gosh

  • there's a very important mouse click

  • coming through now!

  • Let's drop everything now and deal with that!"

  • There are programs for everything

  • that the CPU does.

  • A special program for the mouse,

  • for the clock widget,

  • for the internet radio,

  • and for dealing with letters sent by the keyboard.

  • Each program was initially written by a human

  • in a human-readable programming language,

  • like Java,

  • C++,

  • or Python.

  • But human programs take up a lot of space

  • and contain a lot of unnecessary information to a computer,

  • so they are compiled and made smaller

  • and stored in bits of ones and zeros in memory.

  • The CPU realizes that it needs instructions

  • for how to deal with this mouse click,

  • so it looks up the address for the mouse program

  • and sends a request to the memory subsystem

  • for instructions stored there.

  • Each instruction in the mouse device driver

  • is duly fetched and executed.

  • And that's not nearly the end of the story!

  • Because the CPU learns that the mouse was clicked

  • when the cursor was over a picture

  • of a button on the monitor screen,

  • and so, the CPU asks memory for the monitor program

  • to find out what that button is.

  • And then the CPU has to ask memory

  • for the program for the button,

  • which means that the CPU needs

  • the monitor program again

  • to show the video associated with the button,

  • and so it goes.

  • And let's just say there are a lot of programs involved

  • before you even see the button on the screen

  • light up when you clicked it.

  • So, just the simple task of clicking your mouse

  • means visiting all of the critical components

  • of your computer's architecture:

  • peripherals,

  • the basic input-output system,

  • the CPU,

  • programs,

  • and memory,

  • and not one gremlin.

Do you remember when you first realized

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B1 TED-Ed cpu mouse computer click memory

【TED-Ed】Inside your computer - Bettina Bair

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    阿多賓 posted on 2014/04/24
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