In C/C++, what is an unsigned char
used for? How is it different from a regular char
?
In C++, there are three distinct character types:
char
signed char
unsigned char
char
If you are using character types for text, use the unqualified char
:
'a'
or '0'
(in C++ only, in C their type is int
)"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.
signed char
/ 3. unsigned char
If you are using character types as 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. This might be useful for displaying an octet e.g. as hex value."At least", because 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
.