Signed-Magnitude (S-M)
Signed-Magnitude system is the oldest and simplest solution among negative numbers coding. The most significant bit (MSB) represents the sign of the number. If it is “1” the number is negative, whereas, if it is “0” the number is positive. The range of representation in this system is symmetrical. One of the advantages of this system is its intuitive representation and simplicity of negation. This approach is directly comparable to the common way of showing a sign (placing a "+" or "−" next to the number's magnitude). However, the arithmetical operations are complex in the S-M system. Due to the symmetrical range there is a double representation of zero.
The decimal value of the number represented in the Signed-Magnitude system follows:
Example:
0101 = +5
1101 = -5