What is an unsigned char?

Question

In C/C++, what an unsigned char is used for? How is it different from a regular char?

Answer 1

quoted frome "the c programming laugage" book:

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 2^n, where n is the number of bits in the type. So, for instance, if chars are 8 bits, unsigned char variables have values between 0 and 255, while signed chars have values between -128 and 127 (in a two' s complement machine.) Whether plain chars are signed or unsigned is machine-dependent, but printable characters are always positive.