How to sum the digits of a string?

I have created the following program to sum the digits of a number, that derives from the following expression: op = 2^n, where n is an input. What is wrong with the following code:

n = 5
op = 2^n
g = num2str(op)
b = sum(g(1:end))

Answer 1

[Walter Roberson]

The characters for the digits start from numeric position 48 in the character charts. So '0' is numeric 48 not 0, and '1' is numeric 49, '2' is numeric 50, and so on. When you sum '32' that is '3'+'2' which is 51+50=101 not 5.

Hint: if you subtract '0' from each position in a string of digits then what is left over is the corresponding decimal value. '32' - '0' = [3 2] which can then be added.