ascii标准没规定,但有一些字任集会利用高位为1来扩展ascii字符集,用于显示外国字母和表格菜号。比如说IBM extended character set。
在DOS时代,窗口和菜单边框经常用IBM extended character set来显示,现在图型界面都用不到了。
[解决办法] 4.11.4 Comparison functions
The sign of a nonzero value returned by the comparison functions is determined by the sign of the difference between the values of the first pair of characters (both interpreted as unsigned char ) that differ in the objects being compared.
4.11.4.1 The memcmp function ... 4.11.4.2 The strcmp function