求教C高手

jasmine 2011-03-01 08:52:06

#include <stdio.h>
void main()
{
char c1='a',c2='b',c3='c',c4='\101',c5='\116';
printf("a%cb%c\tc%c\tabc\n",c1,c2,c3);
printf("\tb%c%c\n",c4,c5);
system ("pause");
}
解释一哈第二个printf输出结果的由来

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Wayne-Woo 2011-03-02

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c4='\101',c5='\116'表示八进制的数
将其转换成十进制：
101：1*8^2 + 0*8^1 + 1*8^0 = 65 而65代表的是字符‘A’的ASCII码的值；
116：1*8^2 + 1*8^1 + 6*8^0 = 78 而78代表的是字符‘N’的ASCII码的值；
所以printf("\tb%c%c\n",c4,c5);输出的就是字符AN;

rach09 2011-03-02

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[Quote=引用 1 楼 pengzhixi 的回复:]

8进制转义字符。转换成ascii码值是65和78对应的字符时A和N
[/Quote]
最明确的解释

proghua 2011-03-02

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The final two forms (\0oo and \xhh) are special representations of the ASCII code. To represent a character by its octal ASCII code, precede it with a backslash (\) and enclose the whole thing in single quotes. For example, if your compiler doesn't recognize the alert character (\a), you could use the ASCII code instead:

beep = '\007';

You can omit the leading zeros, so '\07' or even '\7' will do. This notation causes numbers to be interpreted as octal, even if there is no initial 0.

elegant87 2011-03-02

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[Quote=引用 1 楼 pengzhixi 的回复:]

8进制转义字符。转换成ascii码值是65和78对应的字符时A和N
[/Quote]
正解

赵4老师 2011-03-02

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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 marks ('). 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 Specific

There 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 marks. 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.

Syntax

character-constant :

'c-char-sequence'
L'c-char-sequence'

c-char-sequence :

c-char
c-char-sequence c-char

c-char :

any member of the source character set except the single quotation mark ('), backslash (\), or newline character
escape-sequence

escape-sequence :

simple-escape-sequence
octal-escape-sequence
hexadecimal-escape-sequence

simple-escape-sequence : one of

\' \" \? \\
\a \b \f \n \r \t \v

octal-escape-sequence :

\octal-digit
\octal-digit octal-digit
\octal-digit octal-digit octal-digit

hexadecimal-escape-sequence :

\xhexadecimal-digit
hexadecimal-escape-sequence hexadecimal-digit