Number Representation

How do we represent signed (positive & negative) numbers?

Option 1: Sign and Magnitude

• Use left-most bit to represent the sign
• Use other bits to represent the magnitude
• Examples:

          00000001  = +1
          10000001  = -1   (sign & magnitude)
  
          00000101  = +5
          10000101  = -5   (sign & magnitude)
  
          01111111  = +127
          11111111  = -127   (sign & magnitude)

• Problem 1:

          00000000  = +0
          10000000  = -0   (sign & magnitude)

• Problem 2:

          00000101     5
          10000001  + -1
          --------  -----
          10000110    -6  ???