Thread: Signed/Unsigned Chars

Here is one line from C programming language book:

"Whether plain chars are signed or unsigned is machine-dependent, but printable characters are always positive."

My doubt is first of all What does this line means..because suppose my machine has signed chars..How i can i print a character with ASCII value 234 for example because range for signed chars is -128 to +127.

How can compiler interpret 234 correctly and print it as a character in a right way even when it doesn't come under the range.??

The reason it works is that there's only 127 ascii characters.

But C also support extended ASCII character set.

It works when i write

char c = 234;
printf("%c",c);

even when my machine takes above declaration of char as signed.

Yeah, but if you assign for example -2 to a unsigned char it will come out as 254.

Yeah that's wright. but when i write char c = 234 shouldn't it print the character with ASCII value -22 (which is invalid) on my machine but it is printing the character right character.

-22 maps to 234 as unsigned. Trying this "printf("%c\n", -150);" for example will print 'j'.

But that means you should use unsigned chars for extended ascii if char is signed by default, since assigning values larger than 127, does depend on this.

Well, then what's the point of using or caring if a char is signed or not in the context of ascii since all legal values fall with in the positive range of a signed char.

My point was that if you should not depend on the fact that a negative number corresponds to the positive value +127 (not taking into account eventual overflow), then using an unsigned type is not optional.

Originally Posted by ankitsinghal_89

How can compiler interpret 234 correctly and print it as a character in a right way even when it doesn't come under the range.??

The answer lies in the very quote you posted, in red below.

Code:

"Whether plain chars are signed or unsigned is machine-dependent, but printable characters are always positive."

Thanks,i understood it now.

Can you guys explain this also.

If i do something like

int i;
char c;

i = c;

In this case can information be lost ever??I think it information can be lost because it depends on your m/c if it uses sign extension or not while promoting char to int.

What do your guys think??