How are negative numbers represented in 32-bit signed integer?

Question

How are negative number represented in 32-bit signed integer? Is it two's or one's complement? or the last bit on the left is like a flag? For example: (-10)

Answer 1

Usually it's twos-complement.

Answer 2

Most computers these days use two's complement for signed integers, but it can vary by hardware architecture, programming language, or other platform-specific issues.

For a two's-complement representation, the leftmost bit is referred to as the sign bit, and it will be set for a negative integer and clear for a non-negative integer. However, it is more than just a "flag". See the Wikipedia article for more information.

Answer 3

0xFFFFFFFF = -1
0xFFFFFFFE = -2
0xFFFFFFFD = -3
... 

& so on

Answer 4

The most significant bit (last bit on the left) is set for negative numbers.

Answer 5

From the C99 standard:

For signed integer types, the bits of the object representation shall be divided into three groups: value bits, padding bits, and the sign bit. There need not be any padding bits; there shall be exactly one sign bit. Each bit that is a value bit shall have the same value as the same bit in the object representation of the corresponding unsigned type (if there are M value bits in the signed type and N in the unsigned type, then M = N). If the sign bit is zero, it shall not affect the resulting value. If the sign bit is one, the value shall be modified in one of the following ways:

— the corresponding value with sign bit 0 is negated (sign and magnitude);

— the sign bit has the value -(2N) (two’s complement);

— the sign bit has the value -(2N - 1) (ones’ complement).

Which of these applies is implementation-defined, as is whether the value with sign bit 1 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones’ complement), is a trap representation or a normal value. In the case of sign and magnitude and ones’ complement, if this representation is a normal value it is called a negative zero.