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### Course: Computers and the Internet>Unit 2

Lesson 3: Logic gates and circuits

# Circuits & Logic

Adafruit founder Limor Fried and virtual reality designer Nat Brown show how simple logical circuits underlie everything your computer does.

## Want to join the conversation?

• So adders add up the sum of the two numbers (0,1 taken) the first couple of numbers in the 25+50 example make sense 1+0 = 1, 0+0= 0 , but then 1+1 = 0.... and 0+0=1 and sometimes 1+0 = 0 ? Can someone explain why these are different? I can't derive the correct sum (75)
• You know 3+6 = 9 and 8+7 = 15. Note that the second example uses two digits. That was the result of a carry value of 1 from the addition of 8 and 7.

Likewise in binary: 01 + 01 = 10 it has to support carry operations also. That is what you see happening when you see 0+0 = 1 or 1+0 = 0, they are not mentioning the carry operations in the video, but they are present in the circuitry.
(1 vote)
• What do or, xor, and nand do?
Edit what does or, and nand,xor,and not are used for?
• OR tests if a value is true OR false:
true OR true = true
true OR false = true
false OR true = true
It is only false when both are false.
false OR false = false

XOR is either or, not both not neither:
true XOR true = false
true XOR false = true
false XOR true = true
false XOR false = false

NAND is basically what AND does, but inverts it:
true NAND true = false
true NAND false = true
false NAND true = true
false NAND false = false

false NAND false = true

Hope that helped :)
• how do i draw the required logic circuits?
• what wrong when my phone go to the water?
• so the more bits, circuits and adders you have the bigger calculations youre calculator can make on your'e pc?
• Correct!
Programming uses many logic operators to speedily make animations, games, and more!
• If electricity moves at almost the speed of light why would it make any difference if a computer is bigger than another? Since the speed of electricity can orbit the Earth in less than a second, why does it make such a big difference?
• besides speed of light (that's universal) there are other parameters that makes a computer faster than others clock speed is one of them .
Analogy : How fast the pizza is delivered is fixed by speed of light but how fast the pizza is cocked also matter here :-)
• how do circuits make it able to perform tasks in a lightning moment?
• Is there a limit to how many circuits they can use in the computer