# Bits Operations in c++

In this tutorial, i show how to use bits operations in c++ to manipulate bits in programming. Please if you do not understand a particular terminology used here, refer to this link for prior knowledge https://firstclicklimited.com/tutorials/index.php/2021/06/13/binary-representation-of-int-c/

``````int main(){
/////////Bits Operations////////////////

int x,i,A=0,B=0;

//And(&) operations//
//x & y produces 1 only if x and y are set to 1 otherwise produces 0
//10110 & 11010 produces 10010 i.e 22 & 26 produces 18
int y = 22&26;//prints 18
cout<<"Prints 18: "<<y<<"\n\n";
//in binary form
for(i=31;i>=0;i--)
(y&(1<<i))?cout<<"1":cout<<"0";//compare the bit in position
//1 shifted by i places using & operator; if it produces 1,
//then a bit was set in this position. You will see leftshift
//operator later

cout<<"\n\n";

//using the & operator, we can check if a number is even or odd
y &= 1;
cout<<"Prints 0 because y is 18: "<<y<<"\n\n";
y = 23; y &= 1;
cout<<"Prints 1 because y is 23: "<<y<<"\n\n";

//Or(|) operations//
//x | y produces 1 when either x or y or both is set to 1
//10110 & 11010 produces 11110 i.e 22 | 26 produces 30'
y = 22|26;//prints 30
cout<<"Prints 30: "<<y<<"\n\n";
//in binary form
for(i=31;i>=0;i--)
(y&(1<<i))?cout<<"1":cout<<"0";

cout<<"\n\n";

//Xor(^) operations//
//x ^ y produces 1 only if either x or y is set to 1
//Note 1 ^ 1 amounts to 0, only 1 ^ 0 or 0 ^ 1 produces 1
//10110 ^ 11010 produces 01100 i.e 22 | 26 produces 12'
y = 22^26;//prints 12
cout<<"Prints 12: "<<y<<"\n\n";
//in binary form
for(i=31;i>=0;i--)
(y&(1<<i))?cout<<"1":cout<<"0";

cout<<"\n\n";

//Not(~) operations//
//~y produces a number where all the bits of y have been inverted
//~y=-y-1
y = 30;
cout<<"Prints -31: "<<~y<<"\n";
y = ~y;
//in binary form - this will print using Two's complement binary format
for(i=31;i>=0;i--)
(y&(1<<i))?cout<<"1":cout<<"0";

cout<<"\n\n";

//leftshift(<<) operations//
//can be used for appending k zero bits to the number
y = 14;
for(i=31;i>=0;i--)
(y&(1<<i))?cout<<"1":cout<<"0";

cout<<endl;

y = y << 2;

for(i=31;i>=0;i--)
(y&(1<<i))?cout<<"1":cout<<"0";

cout<<endl;

cout<<"y should print 56: "<<y<<endl;
cout<<"\n\n";

//Another use
//use leftshift operator to move n positions through the bit
//for example, to move five places in a 32bit (4 byte) variable (like int in c++) from position 1,
//use 1<<5 - that will start from the least significant bit which is at
//position 0 and move leftwards by 5 places. Please refer to the post
//recommended above for better understanding.
//You have noticed that i have been printing the binary form of a number
//using the << operator to move to the next position to confirm if the bit
//is set to 0 or 1
cout<<"leftshift operation in action\n";
for(i=31;i>=0;i--)
(y&(1<<i))?cout<<"1":cout<<"0";

cout<<"\n\n";

//rightshift(>>) operations//
//do the opposite of leftshift operation with it

////Other Applications of Bits Operations in c++////

//The expression y|1<<2 sets the bit at the 2 bit index to 1
//index starts at 0 - called the least significant bit
//which is the index at the extreme right of the bits
cout<<"y|1<<2 set the bit at index 2 to 1\n";
y = y|1<<2;//start at index 0 and move two places to the left - 1 indicates index 0
for(i=31;i>=0;i--)
(y&(1<<i))?cout<<"1":cout<<"0";

cout<<"\n\n";

//the previous operation has changed y from 56 to some other number
cout<<"y changed from 56 to: "<<y;

cout<<"\n\n";

//Set the bit number in the 2 bit index back to 0
y = y & ~(1<<2);//second bit index to 0
cout<<"bit number at index 2 back to 0\n";
for(i=31;i>=0;i--)
(y&(1<<i))?cout<<"1":cout<<"0";

cout<<"\n\n";

//the previous operation has changed y from 60 bac to 56
cout<<"y changed from 60 back to: "<<y;

cout<<"\n\n";

//Set the bit number in the 2 bit index back to 1
y = y^(1<<2);//this will invert the number at index 2
cout<<"bit number at index 2 back to 1\n";
for(i=31;i>=0;i--)
(y&(1<<i))?cout<<"1":cout<<"0";

cout<<"\n\n";

//the previous operation has changed y from 56 back to 60
cout<<"y changed from 56 back to: "<<y;

cout<<"\n\n";

////////Sets operations using bits manipulation///////

//Each subset of a set (0,1,2,...,n-1,n) corresponds to an
//n bit number where 1 indicate which elements are included
//in the subset
int s[4] = {1,3,4,8};//subset of set (0,1,2,...,n-1,n)
for(i=0;i<4;i++){
A += 1<<s[i];
}
cout<<A<<endl;

//Now confirm that each subset of a set (0,1,2,...,n-1,n)
//corresponds to an n bit number where 1 indicate which
//elements are are included in the subset
cout<<"each subset corresponds to an n bit number\n";
for(i=0;i<32;i++){
if(A&(1<<i))
cout<<i<<" ";
}
cout<<endl;

int a[4] = {3,6,8,9};//subset of set (0,1,2,...,n-1,n)
for(i=0;i<4;i++){
B += 1<<a[i];
}
cout<<B<<endl;

cout<<"\n\nA union B start here\n\n";

int z = A|B;//sum union SUM

for(i=0;i<32;i++){
if(z&(1<<i))
cout<<i<<" ";
}
cout<<"\n";
cout<<__builtin_popcount(z)<<endl;
cout<<__builtin_clz(z)<<endl;//numbers of 0 at the beginning of the bits
cout<<__builtin_ctz(z)<<endl;//numbers of 0 at the end of the bits

for(i=31;i>=0;i--)
(z&(1<<i))?cout<<"1":cout<<"0";

cout<<"\n\nA intersect B start here\n\n";
z = A & B;

for(i=0;i<32;i++){
if(z&(1<<i))
cout<<i<<" ";
}
cout<<"\n";
cout<<__builtin_popcount(z)<<endl;//no of 1s' in the binary number
cout<<__builtin_clz(z)<<endl;//numbers of 0 at the beginning of the bits
cout<<__builtin_ctz(z)<<endl;//numbers of 0 at the end of the bits

for(i=31;i>=0;i--)
(z&(1<<i))?cout<<"1":cout<<"0";

cout<<endl;
}``````

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