What are the differences between bitwise and logical AND operators in C/C++?

A Bitwise And operator is represented as ‘&’ and a logical operator is represented as ‘&&’. The following are some basic differences between the two operators.

a) The logical and operator ‘&&’ expects its operands to be boolean expressions (either 1 or 0) and returns a boolean value. 
The bitwise and operator ‘&’ work on Integral (short, int, unsigned, char, bool, unsigned char, long) values and return Integral value. 

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#include<stdio.h>
int main()
{
    int x = 3;  //...0011
    int y = 7;  //...0111
 
    // A typical use of '&&'
    if (y > 1 && y > x)
      printf("y is greater than 1 AND x\n");
 
    // A typical use of '&'
    int z = x & y;   // 0011
    
    printf ("z = %d", z);
 
    return 0;
}
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Output
y is greater than 1 AND x
z = 3

b) If an integral value is used as an operand for ‘&&’ which is supposed to work on boolean values, the following rule is used in C. 
…..Zero is considered as false and non-zero is considered as true. 

For example in the following program x and y are considered as 1.  



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#include<stdio.h>
// Example that uses non-boolean expression as
// operand for '&&'
int main()
{
   int x = 2, y = 5;
   printf("%d", x&&y);
   return 0;
}
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Output
1

It is compiler error to use the non-integral expression as operand for bitwise &. For example the following program shows compiler error. 

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#include<stdio.h>
// Example that uses non-integral expression as
// operator for '&'
int main()
{
   float x = 2.0, y = 5.0;
   printf("%d", x&y);
   return 0;
}
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Output: 

error: invalid operands to binary & (have 'float' and 'float')

c) The ‘&&’ operator doesn’t evaluate the second operand if the first operand becomes false. Similarly ‘||’ doesn’t evaluate the second operand when first operand becomes true. The bitwise ‘&’ and ‘|’ operators always evaluate their operands. 

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#include<stdio.h>
int main()
{
    int x = 0;
 
    // 'Geeks in &&' is NOT
    // printed because x is 0
    printf("%d\n", (x && printf("Geeks in && ")));
 
    // 'Geeks in &' is  printed
    printf("%d\n", (x & printf("Geeks in & ")));
 
    return 0;
}
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Output
0
Geeks in & 0

The same differences are there between logical OR ‘||’ and bitwise OR ‘|’.

This article is contributed by Ujjwal Jain. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. 

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