binary hexdecimal

Binary is not the same as hexadecimal. So your subject line is strange.

Now about that number. You start at the back. Then you get
0 * 1 = 0
1 * 2 = 2
0 * 4 = 0
0 * 8 = 0
Then add the (decimal) numbers after the equal sign and you get 0010 (start at the bottom) = 2.

With 5 digits it's:
0 * 1 = 0
1 * 2 = 2
0 * 4 = 0
0 * 8 = 0
1 * 16 =16
So you get 10010 = 18.

I leave it to you to extend this to 16 lines for a 16-bit unsigned number.

It's a nice spreadsheet-exercise to break down a string of 16 zeroes and ones into A1 to A16, have the constants 0,2,4,8,16,.32,64 and so on in B1 to B16, calculate the outcome of the multiplications in C1 to c16 and sum that array into the decimal value of the 16 bit binary value you entered somewhere in another cell.

Kees

That's hexadecimal, you just break the binary code into 4 bit clusters. It's normally used in dumps, places like the registry, and for representing text characters internally. Of course inside the computer everything is represented in binary bits (zeros and ones), it's just the way it's used that determines whether it's meant to be a number or a character. And of course if it's a number, there's pure binary and floating point, the latter being used in scientific calculations.
`And remember:
Hexadecimal hits the spot,
16 bits is quite a lot,
twice as much as octal too,
hexadecimal is the byte for you!
`
Happy computing.