Can somebody explain this code?

Question

I got it online. Took it so I could ask about it. Can someone explain in depth how this works?
https://code.sololearn.com/c60Qd55FDaS2/?ref=app

Answer 1

This is simple adder, it's how the electronic logic gates (inside IC) produces arthmetic output.

From the logics, sum of two bits can be obtained by performing XOR (^) of the two bits (a ^ b).
Carry bit can be calculated by AND (&) of two bits (a & b) and shift (<<) the byte to 1bit left.

So we have a = 0011 (3) and b = 0111 (7). then,
------------------------------------------------------------------------------
1st iteration:
sum = 0011 ^ 0111 = 0100

a & b = 0011 & 0111 = 0011
carry = 0011 << 1 = 0110
----------------------------

2nd iteration:
sum = 0100 ^ 0110 = 0010

a & b = 0100 & 0110 = 0100
carry = 0100 << 1 = 1000
----------------------------

3rd iteration:
sum = 0010 ^ 1000 = 1010

a & b = 0010 & 1000 = 0000
carry = 0000 << 1 = 0000
-----------------------------

So finally answer is final value of sum which is 1010 (10).

Answer 2

Are you familiar with bitwise operators?
https://www.sololearn.com/learn/4070/?ref=app

Answer 3

https://en.m.wikipedia.org/wiki/Logic_gate

Answer 4

What's really interesting is how you subtract using gates! 😉

Answer 5

I meant using logic gate example with xor, and, etc

Answer 6

With gates, there are only adder circuits....

Answer 7

This is a good example of how logic gates work. These are the building blocks of digital intehrated circuits. Understanding how they work (and, or, nand, etc. gates) are what make computer work!

Answer 8

If digital devices are composed of logic-gates that only have have adder circuits, how can it do subtraction?

Answer 9

Daniel Cooper Only integers are directly represented by binary bytes.

Answer 10

This article better explains floating point arithmetic operations than I could. We can see there are other steps involved, due to the way floating point values are represented in binary:
https://www.doc.ic.ac.uk/~eedwards/compsys/float/

Finally, note the original code is oriented to integer numbers, as all variables are of type int. Nevertheless, the steps can be applied to integers only.

Answer 11

XOR and AND are the most important logic gates in integrated circuit.

For swapping between a and b using XOR:
a^(a^b) = b
b^(a^b) = a

For investor
a^1 = inverted a

Other usage including parity generator, parity checker and comparator that check for 2 inputs with identical signals or not.

Answer 12

Subtraction is the opposite operation of addition,
int subtract(int a, int b)
{
if (b == 0) return a;
return subtract(a ^ b, (~a & b) << 1);
}

Answer 13

Or

int subtract(int a, int b)
{
if (b == 0) return b;
return subtract(a ^ b, (1^a & b) << 1);
}

Answer 14

note that this method only works for integers

Answer 15

To understand this code u will need to learn bitwiseoparations

https://www.sololearn.com/learn/4070/?ref=app

Answer 16

#include<<iostream>
using namespace std;
int main()
{
int a,b,diff;
cout<<"please insert a and b";
cin>>a>>b;
diff=a-b;
cout<<"diff"<<diff<<endl;

Answer 17

Why wouldn't this work other number types?

Answer 18

Bitwise number series.
😑

Answer 19

cac