Libft(21) - toupper

Libft(21) - toupper

 

TOUPPER(3)               BSD Library Functions Manual               TOUPPER(3)

NAME
     toupper, toupper_l -- lower case to upper case letter conversion

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <ctype.h>

     int
     toupper(int c);

     #include <ctype.h>
     #include <xlocale.h>

     int
     toupper_l(int c, locale_t loc);

DESCRIPTION
     The toupper() function converts a lower-case letter to the corresponding upper-case let-
     ter.  The argument must be representable as an unsigned char or the value of EOF.

     Although the toupper() function uses the current locale, the toupper_l() function may be
     passed a locale directly. See xlocale(3) for more information.

RETURN VALUES
     If the argument is a lower-case letter, the toupper() function returns the corresponding
     upper-case letter if there is one; otherwise, the argument is returned unchanged.

COMPATIBILITY
     The 4.4BSD extension of accepting arguments outside of the range of the unsigned char type
     in locales with large character sets is considered obsolete and may not be supported in
     future releases.  The towupper() function should be used instead.

SEE ALSO
     ctype(3), isupper(3), towupper(3), xlocale(3)

STANDARDS
     The toupper() function conforms to ISO/IEC 9899:1990 (``ISO C90'').

BSD                              July 17, 2005                             BSD

• 소문자 -> 대문자
• a : 97, A : 65 
• 97 - 65 = 32
• 즉, 소문자에서 대문자를 만들기 위해서는 32만큼을 빼주면 된다.
• 소문자인지 확인한 후에 비트 연산으로 'lowercase & 0b11011111' 작업 수행!