What is an unsigned char?

signed char has range -128 to 127; unsigned char has range 0 to 255.

char will be equivalent to either signed char or unsigned char, depending on the compiler, but is a distinct type.

If you're using C-style strings, just use char. If you need to use chars for arithmetic (pretty rare), specify signed or unsigned explicitly for portability.

3 years ago

In C++, there are three distinct character types:

char
signed char
unsigned char

If you are using character types for text, use the unqualified char:

it is the type of character literals like 'a' or '0'.
it is the type that makes up C strings like "abcde"

It also works out as a number value, but it is unspecified whether that value is treated as signed or unsigned. Beware character comparisons through inequalities - although if you limit yourself to ASCII (0-127) you're just about safe.

If you are using character types like numbers, use:

signed char, which gives you at least the -127 to 127 range. (-128 to 127 is common)
unsigned char, which gives you at least the 0 to 255 range.
The C++ standard only gives the minimum range of values that each numeric type is required to cover. sizeof (char) is required to be 1 (i.e. one byte), but a byte could in theory be for example 32 bits. sizeof would still be report its size as 1 - meaning that you could have sizeof (char) == sizeof (long) == 1.

3 years ago