What does #ifdef mean in C?
What does #ifdef mean in C?
Description. In the C Programming Language, the #ifdef directive allows for conditional compilation. The preprocessor determines if the provided macro exists before including the subsequent code in the compilation process.
What are the various conditional syntax of preprocessor in C?
The preprocessor conditional compilation directive spans several lines: The condition specification line (beginning with #if , #ifdef , or #ifndef ) Lines containing code that the preprocessor passes on to the compiler if the condition evaluates to a nonzero value (optional) The #elif line (optional)
How do I use #ifdef in C++?
#ifdef means if defined. If the symbol following #ifdef is defined, either using #define in prior source code or using a compiler command-line argument, the text up to the enclosing #endif is included by the preprocessor and therefore compiled. #if works similarly, but it evaluates the boolean expression following it.
What does #ifdef mean in C++?
if defined
#ifdef means if defined. If the symbol following #ifdef is defined, either using #define in prior source code or using a compiler command-line argument, the text up to the enclosing #endif is included by the preprocessor and therefore compiled. #if works similarly, but it evaluates the boolean expression following it.
What is the use of the preprocessor in C?
The C preprocessor is a macro processor that is used automatically by the C compiler to transform your program before actual compilation. It is called a macro processor because it allows you to define macros , which are brief abbreviations for longer constructs. The C preprocessor provides four separate facilities that you can use as you see fit:
What are preprocessor directives in C programming?
Preprocessor Directives – C Programming #include. The #include preprocessor directive is used to paste code of given file into current file. Macro’s (#define) Let’s start with macro, as we discuss, a macro is a segment of code which is replaced by the value of macro. #undef. To undefine a macro means to cancel its definition. #ifdef. #ifndef. #if. #else. #error. #pragma.
Is the C preprocessor a separate program?
The preprocessor provides the ability for the inclusion of header files, macro expansions, conditional compilation, and line control. The C Preprocessor is not a part of compiler, it is a separate program invoked by the compiler as the first part of translation.
What does C compiler mean?
Compiling a C Program Compiling is the transformation from Source Code (human readable) into machine code (computer executable). A compiler is a program.