conditional compilation in c

What is a conditional compilation in c

Conditional compilation: conditional compilation reduce the executable file 

Conditional compilation is a feature in the C programming language that allows developers to selectively compile code based on certain conditions. This can be useful for writing code that can be customized for different environments or platforms, or for disabling certain code during development or debugging.

In C, conditional compilation is achieved through the use of preprocessor directives, which are special commands that are processed by the compiler before the actual compilation of code begins. The most commonly used directive for conditional compilation is #ifdef, which tests whether a particular macro has been defined, and only compiles the code that follows if it has.

For example, suppose you have a program that needs to run on multiple platforms, each with its own set of specific features. You could use conditional compilation to include platform-specific code in your program, like this:

#ifdef PLATFORM_A
   // code specific to platform A
#elif PLATFORM_B
   // code specific to platform B
#else
   // default code
#endif

In this example, PLATFORM_A and PLATFORM_B are macros that are defined elsewhere in the code or through a command-line argument when compiling the program. The code within the #ifdef block will only be compiled if the PLATFORM_A macro is defined, and so on.

Conditional compilation can also be used for debugging purposes. For example, you could use a macro like DEBUG to selectively compile debugging code, like this:

#ifdef DEBUG
   // debugging code
#endif

In this case, the debugging code will only be compiled if the DEBUG macro is defined.

Overall, conditional compilation is a powerful feature in C that allows developers to customize and optimize their code for different environments and situations. However, it can also make code more complex and harder to read if used excessively, so it is important to use it judiciously and with good coding practices.

Advantage: reduce the executable file

Disadvantage: Run time we can't change the only decide compilation times