Box-drawing characters
`#define VBAR "\u2502"` names a vertical bar for use in a C string. The four hexadecimal digits identify the character; they are not four characters to print. section 14.3
TAKEAWAY: A Unicode escape specifies a Unicode code point in C source using `\u` or `\U` followed by hexadecimal digits. It lets a string literal name a character without placing that character directly in the source. Specifying it is distinct from displaying it: the multibyte printing example switches locale before printing. 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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Compare the escapes used for vertical, horizontal, and corner characters in string-literal macros. section 14.3
