Difference between an unsigned and a signed type?

The qualifier signed or unsigned may be applied to char or any integer. unsigned numbers are always positive or zero, and obey the laws of arithmetic modulo 2n, where n is the number of bits in the type. So, for instance, if charsare 8 bits, unsigned charvariables have values between 0 and 255, while signed charshave values between -128 and 127 (in a two's complement machine.) Whether plain charsare signed or unsigned is machine-dependent, but printable characters are always positive.