A printed A does not uniquely identify a character. “Latin capital letter A” can have different printed forms, while “Greek capital letter Alpha” can look similar. Unicode, also called ISO 10646 here, identifies character concepts as code points rather than treating glyphs as identities. It also records properties and relationships, such as whether a character is a capital letter. section 14.3
43 #define VBAR "\u2502" /**< a vertical bar character */
44 #define HBAR "\u2500" /**< a horizontal bar character */
45 #define TOPLEFT "\u250c" /**< topleft corner character */
46 #define TOPRIGHT "\u2510" /**< topright corner character */
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These C string macros use Unicode escapes for horizontal and vertical lines and box corners. The escapes identify characters without requiring those characters on the keyboard. section 14.3
TAKEAWAY: A code point identifies a character concept, not its printed shape or the bytes used to represent it. C programs handling such characters as multibyte strings may need a locale for printing and an mbstate_t parsing state when scanning them. section 14.3
