Preprocessor
directives are lines included in the code of our programs that are not program
statements but directives for the preprocessor. These lines are always preceded
by a hash sign (#). The preprocessor is executed before the actual compilation
of code begins, therefore the preprocessor digests all these directives before
any code is generated by the statements.
These preprocessor directives extend only across a
single line of code. As soon as a newline character is found, the preprocessor
directive is considered to end. No semicolon (;) is expected at the end of a
preprocessor directive. The only way a preprocessor directive can extend
through more than one line is by preceding the newline character at the end of
the line by a backslash (\).
macro definitions (#define, #undef)
Conditional inclusions (#ifdef, #ifndef, #if, #endif,
#else and #elif)
Line control (#line)
Error directive (#error)
Source file inclusion (#include)
Pragma directive (#pragma)
阅读(139) | 评论(0) | 转发(0) |
