The third encoding method is two's complement. For example, if we have the number 93, which is 01011101b in binary, then after bitwise not this number becomes 10100010b, which is negative -93. This operation replaces all zeros with ones and all ones with zeros. The positive numbers in this method are the same as in the sign bit method but the negative numbers are created by applying the bitwise not operation to positive numbers. The second method of representation is one's complement. As you can see, the first bit is flipped from 0 to 1 and that also flips the sign of the number.
For example, 01011101b is a positive number because the first bit is '0' and the remaining bits are 1011101b, which is equal to 93 in decimal, therefore this number is +93. The remaining bits show the absolute value of the number. You can think of '0' as '+' and '1' as '-'. If the number is negative, then the leftmost bit is set to '1'. If the integer is positive, then the leftmost bit is set to '0'. In this method, the most significant bit (leftmost bit) is used as the sign of the number. It's the simplest way to encode a signed integer to binary. We have implemented five different signed number representations. Therefore, negative numbers in binary are represented in special binary schemes that encode the minus sign to a bit pattern. The binary number system has only two symbols '0' and '1', and unlike the decimal number system, there is no negative sign '-'.
This tool converts negative decimal numbers (and also positive) to the binary numeral system.