Checking if a bit is set or not

Question

How to check if a certain bit in a byte is set?

bool IsBitSet(Byte b,byte nPos)
{
   return .....;
}

Answer 1

sounds a bit like homework, but:

bool IsBitSet(byte b, int pos) {    return (b & (1 << pos)) != 0; } 

pos 0 is least significant bit, pos 7 is most.

Answer 2

Based on Mario Fernandez's answer, I thought why not have it in my toolbox as a handy extension method not limited to datatype, so I hope it's OK to share it here:

/// <summary> /// Returns whether the bit at the specified position is set. /// </summary> /// <typeparam name="T">Any integer type.</typeparam> /// <param name="t">The value to check.</param> /// <param name="pos"> /// The position of the bit to check, 0 refers to the least significant bit. /// </param> /// <returns>true if the specified bit is on, otherwise false.</returns> public static bool IsBitSet<T>(this T t, int pos) where T : struct, IConvertible {  var value = t.ToInt64(CultureInfo.CurrentCulture);  return (value & (1 << pos)) != 0; } 

Note: Do not use for performance critical operations, as this method always converts to long.

Answer 3

Equivalent to Mario F code, but shifting the byte instead of mask:

bool IsBitSet(byte b, int pos)
{
   return ((b >> pos) & 1) != 0;
}

Answer 4

Here is the solution in words.

Left shift an integer with initial value 1 n times and then do an AND with the original byte. If the result is non-zero, bit is Set otherwise not. :)

Answer 5

This also works (tested in .NET 4):

void Main()
{
    //0x05 = 101b
    Console.WriteLine(IsBitSet(0x05, 0)); //True
    Console.WriteLine(IsBitSet(0x05, 1)); //False
    Console.WriteLine(IsBitSet(0x05, 2)); //True
}

bool IsBitSet(byte b, byte nPos){
    return new BitArray(new[]{b})[nPos];
}

Answer 6

Right shift your input n bits down and mask with 1, then test whether you have 0 or 1.

Answer 7

something like

return ((0x1 << nPos) & b) != 0