Why does this code result in printing out -106? Is there any way I can easily make test3 into the correct value of 150, or is it just stupid using chars like this?Code:char test1 = 15; char test2 = 10; char test3 = test1*test2; printf("%d ", test3);
Chars are signed by default [in most compilers] and any value with the highest bit set (that is, a value above 127 in most architectures) will be considered a negative number. In this case, 150 is bigger than 127, so it is treated as a negative number - essentially 150-256 => -106
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Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers.
The value of char in C is (-128 -> 127), or using unsigned char instead of char if you want 150.
Last edited by bbebfe; 11-20-2008 at 06:08 AM.
Do you know why bbebfe is NOT bbebfe?
This is of course not GUARANTEED (a DEC-10 would perhaps have 4 chars per 36-bit word -> 9 bit per char and a range of -256..255, to give an example), but yes, it's negative because it's above the positive range of the char numbers in this architecture.Originally Posted by bbebfe
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Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers.
Is there such a thing as unsigned char, like with int?
Never mind, took me 30 secs to test it myself, thanks for the answers.
matsp is right， How max and min of a type, there is no definite value within C, It's depends on the C compiler and target system. You can get the max and min value of char by referring the CHAR_MAX and CHAR_MIN macros defined in <limits.h>
Code:printf("max=%d, min=%d\n", CHAR_MAX, CHAR_MIN);
Do you know why bbebfe is NOT bbebfe?
> Chars are signed by default
Without qualification, whether a 'char' is signed or unsigned is implementation-specific.
gcc (for example) has a flag to change the behaviour, should it happen to matter.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
Yes, that's why I put "[in most compilers]". And I know a few other compilers also have an option to make char unsigned by default. I don't know of a compiler that without flags make char unsigned, but I wouldn't be surprised if they do exist.
--
Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers.
