C++ Character Constants Character constants are one or more members of the “source character set,” the character set in which a program is written, surrounded by single quotation s ('). They are used to represent characters in the “execution character set,” the character set on the machine where the program executes.Microsoft Specific For Microsoft C++, the source and execution character sets are both ASCII.END Microsoft SpecificThere are three kinds of character constants: Normal character constants Multicharacter constants Wide-character constants Note Use wide-character constants in place of multicharacter constants to ensure portability.Character constants are specified as one or more characters enclosed in single quotation s. For example:char ch = 'x'; // Specify normal character constant. int mbch = 'ab'; // Specify system-dependent // multicharacter constant. wchar_t wcch = L'ab'; // Specify wide-character constant.Note that mbch is of type int. If it were declared as type char, the second byte would not be retained. A multicharacter constant has four meaningful characters; specifying more than four generates an error message.Syntaxcharacter-constant :'c-char-sequence' L'c-char-sequence'c-char-sequence :c-char c-char-sequence c-charc-char :any member of the source character set except the single quotation ('), backslash (\), or newline character escape-sequenceescape-sequence :simple-escape-sequence octal-escape-sequence hexadecimal-escape-sequencesimple-escape-sequence : one of\' \" \? \\ \a \b \f \n \r \t \voctal-escape-sequence :\octal-digit \octal-digit octal-digit \octal-digit octal-digit octal-digithexadecimal-escape-sequence :\xhexadecimal-digit hexadecimal-escape-sequence hexadecimal-digitMicrosoft C++ supports normal, multicharacter, and wide-character constants. Use wide-character constants to specify members of the extended execution character set (for example, to support an international application). Normal character constants have type char, multicharacter constants have type int, and wide-character constants have type wchar_t. (The type wchar_t is defined in the standard include files STDDEF.H, STDLIB.H, and STRING.H. The wide-character functions, however, are prototyped only in STDLIB.H.)The only difference in specification between normal and wide-character constants is that wide-character constants are preceded by the letter L. For example:char schar = 'x'; // Normal character constant wchar_t wchar = L'\x81\x19'; // Wide-character constantTable 1.2 shows reserved or nongraphic characters that are system dependent or not allowed within character constants. These characters should be represented with escape sequences.Table 1.2 C++ Reserved or Nongraphic CharactersCharacter ASCII Representation ASCII Value Escape Sequence Newline NL (LF) 10 or 0x0a \n Horizontal tab HT 9 \t Vertical tab VT 11 or 0x0b \v Backspace BS 8 \b Carriage return CR 13 or 0x0d \r Formfeed FF 12 or 0x0c \f Alert BEL 7 \a Backslash \ 92 or 0x5c \\ Question ? 63 or 0x3f \? Single quotation ' 39 or 0x27 \' Double quotation " 34 or 0x22 \" Octal number ooo — \ooo Hexadecimal number hhh — \xhhh Null character NUL 0 \0 If the character following the backslash does not specify a legal escape sequence, the result is implementation defined. In Microsoft C++, the character following the backslash is taken literally, as though the escape were not present, and a level 1 warning (“unrecognized character escape sequence”) is issued.Octal escape sequences, specified in the form \ooo, consist of a backslash and one, two, or three octal characters. Hexadecimal escape sequences, specified in the form \xhhh, consist of the characters \x followed by a sequence of hexadecimal digits. Unlike octal escape constants, there is no limit on the number of hexadecimal digits in an escape sequence.Octal escape sequences are terminated by the first character that is not an octal digit, or when three characters are seen. For example:wchar_t och = L'\076a'; // Sequence terminates at a char ch = '\233'; // Sequence terminates after 3 charactersSimilarly, hexadecimal escape sequences terminate at the first character that is not a hexadecimal digit. Because hexadecimal digits include the letters a through f (and A through F), make sure the escape sequence terminates at the intended digit.Because the single quotation (') encloses character constants, use the escape sequence \' to represent enclosed single quotation s. The double quotation (") can be represented without an escape sequence. The backslash character (\) is a line-continuation character when placed at the end of a line. If you want a backslash character to appear within a character constant, you must type two backslashes in a row (\\). (SeePhases of Translation in the Preprocessor Reference for more information about line continuation.)
CFileDialog Open(TRUE, _T("*.txt"), NULL, OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT, _T("帐号文件 (*.txt)|*.txt|All Files (*.*)|*.*||"), NULL);
if (Open.DoModal() == IDOK)
{
strPath = Open.GetPathName();//这就是你要的路径了。
} CStdioFile file;
if (!file.Open(strPath, CFile::modeReadWrite))
{
//找开文件失败
AfxMessageBox("帐号文件错误");
return;
}
Character constants are one or more members of the “source character set,” the character set in which a program is written, surrounded by single quotation s ('). They are used to represent characters in the “execution character set,” the character set on the machine where the program executes.Microsoft Specific For Microsoft C++, the source and execution character sets are both ASCII.END Microsoft SpecificThere are three kinds of character constants: Normal character constants
Multicharacter constants
Wide-character constants
Note Use wide-character constants in place of multicharacter constants to ensure portability.Character constants are specified as one or more characters enclosed in single quotation s. For example:char ch = 'x'; // Specify normal character constant.
int mbch = 'ab'; // Specify system-dependent
// multicharacter constant.
wchar_t wcch = L'ab'; // Specify wide-character constant.Note that mbch is of type int. If it were declared as type char, the second byte would not be retained. A multicharacter constant has four meaningful characters; specifying more than four generates an error message.Syntaxcharacter-constant :'c-char-sequence'
L'c-char-sequence'c-char-sequence :c-char
c-char-sequence c-charc-char :any member of the source character set except the single quotation ('), backslash (\), or newline character
escape-sequenceescape-sequence :simple-escape-sequence
octal-escape-sequence
hexadecimal-escape-sequencesimple-escape-sequence : one of\' \" \? \\
\a \b \f \n \r \t \voctal-escape-sequence :\octal-digit
\octal-digit octal-digit
\octal-digit octal-digit octal-digithexadecimal-escape-sequence :\xhexadecimal-digit
hexadecimal-escape-sequence hexadecimal-digitMicrosoft C++ supports normal, multicharacter, and wide-character constants. Use wide-character constants to specify members of the extended execution character set (for example, to support an international application). Normal character constants have type char, multicharacter constants have type int, and wide-character constants have type wchar_t. (The type wchar_t is defined in the standard include files STDDEF.H, STDLIB.H, and STRING.H. The wide-character functions, however, are prototyped only in STDLIB.H.)The only difference in specification between normal and wide-character constants is that wide-character constants are preceded by the letter L. For example:char schar = 'x'; // Normal character constant
wchar_t wchar = L'\x81\x19'; // Wide-character constantTable 1.2 shows reserved or nongraphic characters that are system dependent or not allowed within character constants. These characters should be represented with escape sequences.Table 1.2 C++ Reserved or Nongraphic CharactersCharacter ASCII
Representation ASCII
Value Escape Sequence
Newline NL (LF) 10 or 0x0a \n
Horizontal tab HT 9 \t
Vertical tab VT 11 or 0x0b \v
Backspace BS 8 \b
Carriage return CR 13 or 0x0d \r
Formfeed FF 12 or 0x0c \f
Alert BEL 7 \a
Backslash \ 92 or 0x5c \\
Question ? 63 or 0x3f \?
Single quotation ' 39 or 0x27 \'
Double quotation " 34 or 0x22 \"
Octal number ooo — \ooo
Hexadecimal number hhh — \xhhh
Null character NUL 0 \0
If the character following the backslash does not specify a legal escape sequence, the result is implementation defined. In Microsoft C++, the character following the backslash is taken literally, as though the escape were not present, and a level 1 warning (“unrecognized character escape sequence”) is issued.Octal escape sequences, specified in the form \ooo, consist of a backslash and one, two, or three octal characters. Hexadecimal escape sequences, specified in the form \xhhh, consist of the characters \x followed by a sequence of hexadecimal digits. Unlike octal escape constants, there is no limit on the number of hexadecimal digits in an escape sequence.Octal escape sequences are terminated by the first character that is not an octal digit, or when three characters are seen. For example:wchar_t och = L'\076a'; // Sequence terminates at a
char ch = '\233'; // Sequence terminates after 3 charactersSimilarly, hexadecimal escape sequences terminate at the first character that is not a hexadecimal digit. Because hexadecimal digits include the letters a through f (and A through F), make sure the escape sequence terminates at the intended digit.Because the single quotation (') encloses character constants, use the escape sequence \' to represent enclosed single quotation s. The double quotation (") can be represented without an escape sequence. The backslash character (\) is a line-continuation character when placed at the end of a line. If you want a backslash character to appear within a character constant, you must type two backslashes in a row (\\). (SeePhases of Translation in the Preprocessor Reference for more information about line continuation.)