Signed to Unsigned and Vice Versa (arithmetical)

Question

How to convert a number from unsigned to signed?

signed: -32768 to 32767 unsigned: 0 to 65535

I am solving the problem in JavaScript. The situation is that I

Answer 1

function signed(bits, value) { return value & (1 << (bits - 1)) ? value - (1 << bits) : value; }

signed(8, 0xFF); // returns -1

signed(16, 0xFF); // returns 255