5 return isalpha(c) || isdigit(c);
10 return isupper(c) || islower(c);
15 return c == ' ' || c == '\t';
20 return c >= '0' && c <= '9';
25 return c >= 'A' && c <= 'Z';
30 return c >= 'a' && c <= 'z';
35 return c > ' ' && c <= '~';
40 return isgraph(c) || c == ' ';
45 return isblank(c) || c == '\f' || c == '\n' || c == '\r' || c == '\v';
50 return islower(c) ? (c + ('A' - 'a')) : c;
55 return isupper(c) ? (c - ('A' - 'a')) : c;