i don't understand how 15 = 00001111 so how do i do the bin thing???????????????????????????????????????????????????????

# 7/14 can some one help me on "a bit of this and that"

**0xmoonstar**#2

```
It's like this: 0 0 0 0 1 1 1 1
-------------------------
index/exponents: 7 6 5 4 3 2 1 0
```

If there is 1 it means that this bit is set. If you look at the index you can see that **bit 0, 1, 2 and 3** are set.

The base in this calculation is 2**exponent/index

We said that **0,1,2 and 3 are set**.

We have to do this calculation:

```
2**0 + 2**1 + 2**2 + 2**3 = ?
-----------------------------
Equal to: 1 + 2 + 4 + 8 = 15
```

print bin(0b1110 & 0b101)

Look back to the lesson where you counted to 12 (lesson 3 in binary representation. Top that up to 15 and you should see how it works.