Q:

# C program to check whether all bits of a number are UNSET/LOW?

Give a number of one byte (8 bits) and we have to check whether all bits are UNSET/LOW.

Example -1

```Input number: 0
Binary value: 00000000
Output: Yes, all bits are unset
```

Example -2

```Input number: 50
Binary value: 00110011
Output: No, all bits are not unset
```

To solved this program, we will use BITWISE AND (&) operator, we will traverse bits from 7 to 0 (in case of two bytes number, it would be 15 to 0 and so on...) and check if there is any SET/HIGH bit, then we will break the loop and output will be false that means "all bits are not UNSET/LOW".

Consider the program:

``````#include <stdio.h>

//function to check whether all bits are
//UNSET/LOW or not?
int isAllBitsUnset(unsigned int num)
{
int loop, cnt=0;

for(loop=7; loop>=0; loop--)
{
//check, if there is any SET/HIGH bit
if( num & (1<<loop))
{
cnt =1;
break;
}
}
if(cnt==0)
return 1; //true
else
return 0; //false
}

//main function
int main()
{
unsigned int number;

printf("Enter an integer number (between 0-255): ");
scanf("%d",&number);

if(isAllBitsUnset(number))
printf("All bits are UNSET/LOW.\n");
else
printf("All bits are not UNSET/LOW.\n");

return 0;
}``````

Output

```First Run:

Enter an integer number (between 0-255): 0
All bits are UNSET/LOW.

Second Run:

Enter an integer number (between 0-255): 50
All bits are not UNSET/LOW.
```

We wrote a function int isAllBitsUnset(unsigned int num), it is taking an unsigned integer type number as an argument and returning 0 if all bits are not UNSET/LOW and 1 if all bits are UNSET/LOW.

function:

``````int isAllBitsUnset(unsigned int num)
{
int loop, cnt=0;

for(loop=7; loop>=0; loop--)
{
//check, if there is any SET/HIGH bit
if( num & (1<<loop))
{
cnt =1;
break;
}
}
if(cnt==0)
return 1; //true
else
return 0; //false
}``````

To check the bits, we are traversing loop from 7 to 0 (in case of 8 bits) and checking each bit, whether it is HIGH/SET or not, if any bit is HIGH/SET then value of cnt will be 1 (which is 0 initially, cnt is using as a flag variable) and loop will break.