# Convert a Bitstring into an integer value

I have got a String filled up with 0 and 1 and would like to get an Integer out of it:

``````String bitString = "";
int Number;
int tmp;

bitString = "";
for (i=1;i<=10;i++)
{
bitString +=  tmp % 2;
delay(50);
}
// now bitString contains for example "10100110"
// Number = bitstring to int <-------------
// In the end I want that the variable Number contains the integer 166
``````
• What is the question? What do you expect this code to do and what is it doing? What else have you tried? – Craig May 12 '14 at 18:42
• @Craig I eddited the question. For example If the bitString contains a "10100110" I want the programm to save it as the decimal 166 in the int variable. – kimliv May 12 '14 at 18:46
• Do you need the string? You could create the integer representation directly. – Craig May 12 '14 at 19:14
• @Craig i would also like to print out the bitstring – kimliv May 12 '14 at 19:15

If you only need the string for printing you can store value in an integer and then use the Serial.print(number,BIN) function to format the output as a binary value. Appending integers to strings is a potentially costly operation both in performance and memory usage.

``````int Number = 0;
int tmp;

for (int i=9;i>=0;i--) {
Number += (tmp % 2) << i;
delay(50);
}
Serial.print(Number, BIN);
``````
• Yes your solution looks more efficient! and does the work – kimliv May 12 '14 at 19:36

Check out `strtoul()`

It should work something like this:

`unsigned long result = strtoul(bitstring.c_str(), NULL, 2);`

Now you have a long variable which can be converted into an int if needed.

• @kimliv Did you add .c_str() to the end of bitstring as Peter pointed out above? c_str() should return a const char*. – Doowybbob May 12 '14 at 19:22
• it is working that way! – kimliv May 12 '14 at 19:25