CODEWITHSUNDEEP
c#bit-manipulation
AaronParkes
AaronParkes

Reputation: 311

Trying to get 0 or 1 in bitwise but get 64 or 32 instead

Following an exercise and I am trying to obtain in an integer, whether a bit is 0 or 1 in a certain position.

Here is my code so far:

Console.WriteLine("input number");
int number = int.Parse(Console.ReadLine());

Console.WriteLine("input position");
int position = int.Parse(Console.ReadLine());

int place = 1;
int bit = place << position;
Console.WriteLine(bit);

So the user inputs a number (the integer, lets say 10) then a bit position (lets say 5) and the program should tell me if or not the 5th bit (from the right) is a 0 or one.

However instead its telling me the value that bit represents (1, 2, 4, 8, 16, 32, 64 etc.)

I really am uncertain what i've missed, I went ahead and looked up the solution (which I realised did not need user input) and that gave me the same error.

int n = 35;
int p = 6; 
int i = 1; 
int mask = i << p;

The question, quote, says "Value of the bit on the position p in the number (0 or 1)." so it wants 0 or 1 as output. So I'm stumped, really need some help please. I may be overthinking things and missing something obvious but I've failed to find a solution.

Upvotes: 1

Views: 123

Answers (3)

Lionel D
Lionel D

Reputation: 317

you do a bit shift: http://msdn.microsoft.com/fr-fr/library/a1sway8w.aspx

i think you should test your bit with the following code:

if(valueToTest & 32 == 32) => Bit is active

Upvotes: 0

Selman Gen&#231;
Selman Gen&#231;

Reputation: 101681

You need bitwise AND & operator

int place = 1;
int bit = place << position;

if((number & bit) == bit)  Console.WriteLine("{0}. bit is 1",position);
else Console.WriteLine("{0}. bit is 0", position);

Upvotes: 1

Tim S.
Tim S.

Reputation: 56536

int n = 35;
int p = 6; 
int i = 1; 
int mask = i << p;

At this point, you have the mask == 64, and n == 35. Now you need to check or apply the mask in some way. A good way to do this is with the & operator, which is a bitwise AND. In the case of a mask with one bit set to 1 (like your mask), this will tell you whether n has that bit set to 1 or 0.

int masked = n & mask;
// masked will be 0 or 64; since we want 0 or 1...
int result = masked != 0 ? 1 : 0;
// although I'd go with a bool if possible, because it makes more sense
bool boolResult = masked != 0;

Upvotes: 1

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