Character data type

[rathorek]

Hello everyone,

Actually I don't have question, but I get confused with character data type in C language. In one book I read that

Data type range
char -128 to 127
unsigned char 0 to 255

In C char is data type which has ASCII values associated with it and ASCII values are positive. It is true or not. Please help me.

Thank you,
rathorek

[ayousuf]

Yes, ASCII values are always positive ranging from 0 to 255.

You can see the characters associated with them here: http://www.lookuptables.com/

Ascii values are the same as Dec

[Danny]

Not quite. First off, char isn't necessarily ASCII. On IBM machines it's EBCDIC and theoretically, it could be any byte-sized encoding.
Secondly, ASCII values can be negative. This happens when you try to queeze 255 ASCII code into a signed char. Why do that? Supporting a multilingual system, say Hebrew and English, requires that some characters be mapped to negative values if char is signed by default. From my own experience, it works pretty well.

[jonnin]

ASCII was 0-127 initially as well, the second "half" was added much later on.

[Danny]

ASCII was indeed a 128 sign system originally. However, EBCDIC began as a 225 symbol system so it has always needed at least 8 bits. Histroically, EBCDIC was based on BCDIC which used 6 bits (IIRC) back in the days of mechanical computing machines of the 1920s and 1930s. But the point is: char isn't necessarily 8 bits long, char isn't necessarily an ASCII value, and (extended) ASCII values can be negative.

[rathorek]

Thanks to all for your reply.

rathorek