Signed number Representation and Bitwise NOT In C Language

In C, signed numbers are represented using two's complement representation. In this representation, the leftmost bit (also known as the most significant bit) is used to indicate the sign of the number. A value of 0 indicates a positive number, while a value of 1 indicates a negative number. The remaining bits are used to represent the magnitude of the number.

The bitwise NOT operator (~) inverts the bits of the operand. It can be applied to both signed and unsigned numbers, and will invert the bits of the number regardless of whether it is positive or negative.

For example, if a signed number is represented using 8 bits, the bitwise NOT of the number 5 (00000101) would be 11111010, which is equivalent to -6 in two's complement representation. However, it is important to note that the bitwise NOT of a negative number doesn't change the sign of the number, it will only change the magnitude.

It is also important to note that when using the bitwise NOT operator on a signed number, the result will be an unsigned number, and it may cause unexpected results if it is used in a context where a signed number is expected.

It's also worth mentioning that C standard defines that when performing a bitwise operation with a signed operand, the operand shall be converted to unsigned type before the operation. This can lead to unexpected behavior if the number is negative and the programmer doesn't take this into account.