c++ - Negative ASCII value

Question

What's the point of negative ASCII values?

int a = '?'; //a = -85 but as in ASCII table '<<' should be 174

Answer 1

There are no negative ASCII values. ASCII includes definitions for 128 characters. Their indexes are all positive (or zero!).

You're seeing this negative value because the character is from an Extended ASCII set and is too large to fit into the char literal. The value therefore overflows into the bit of your char (signed on your system, apparently) that defines negativeness.

The workaround is to write the value directly:

unsigned char a = 0xAE; // ?

I've written it in hexadecimal notation for convention and because I think it looks prettier than 174. :)