Is char unsigned by default?

I've seen a lot of "unsigned char" in the past, but is it already unsigned by default or is it implementation specific?

It is implementation specific.

Usually I think it is signed by default, however, which is why you will see "unsigned char" used in a lot of code.

It is implementation specific as previously mentioned.


Quzah.

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Originally Posted by MK27

Usually I think it is signed by default, however, which is why you will see "unsigned char" used in a lot of code.

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I think that the real reason 'why you will see "unsigned char" used in a lot of code' is that the code involved requires the use of unsigned integers for correctness, e.g., bit shifting. Thus, it makes sense to specify unsigned char rather than assuming that the implementation will have char as unsigned.

Ah, so I guess the moral of the story is specify it anyway if it's important - even if it's just being clear to other developers that you intend this to be unsigned.

char is always unsigned. for example if u give char a=-257 it wont bother about '-'. it will simply print value of corresponding to char 1, some special symbol.

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Originally Posted by magestrium

char is always unsigned.

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Sorry, but the 1999 edition of the C standard disagrees with you, so you must be wrong:

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Originally Posted by C99 Section 6.2.5 Paragraph 15 and note 35

The three types char, signed char, and unsigned char are collectively called the character types. The implementation shall define char to have the same range, representation, and behavior as either signed char or unsigned char.

CHAR_MIN, defined in <limits.h>, will have one of the values 0 or SCHAR_MIN, and this can be used to distinguish the two options. Irrespective of the choice made, char is a separate type from the other two and is not compatible with either.

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Originally Posted by magestrium

for example if u give char a=-257 it wont bother about '-'. it will simply print value of corresponding to char 1, some special symbol.

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Your example has to do with how the value is printed, not with whether char is signed or unsigned.

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Originally Posted by laserlight

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Originally Posted by magestrium

char is always unsigned

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Sorry, but the 1999 edition of the C standard disagrees with you, so you must be wrong:

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Just to expand on that: the 1989 C standard and the C++ standard also specify (albeit in slightly different prose) that it is implementation defined whether char is unsigned or signed.

Wotcher,

I needed to know, so I wrote a quick program and tested it on our various porting platforms. The following platforms all have char == signed char:
Windoze, Solaris(sparc), Solaris(intel), HP(risc), HP(intel), Linux(intel).

IBM, however, buck the tend. All these platforms have char == unsigned char:
Aix, Linux(s390), Linux(PowerPC).

Hope that helps,

Grelly

Actually it's configurable in Visual Studio IIRC.

Microsoft compilers have a flag to change it
/J (Default char Type Is unsigned) (C++)

GCC compilers have a flag to change it
Options Controlling C Dialect

If you really care about the signed-ness of your chars, then just say "signed char" or "unsigned char" and forget about whether your current compiler has a flag to fix it for you.

I can't help feeling that to use compiler options to change a default behaviour is a bad idea. It won't be obvious to the next developer that the sign-ness has been reversed.

My recommendation is to get into the habit of using the signed/unsigned qualifiers the whole time.