5. Signed Integers

• We also need to be able to represent negative quantities.

• In arithmetics, a minus sign is used as a prefix in notation of negative numbers.

• In a combination of bits, a leftmost bit could indicate the sign.

• Therefore,

  • one half of integer numbers could represent positive numbers,

  • another half - negative numbers.

• Decision to make: what codes should we assign to what values?

• Positive numbers and zero can be presented in a straightforward positional scheme.

• For example, largest positive member of a 5-bit pattern is 01111, or decimal 15.