16.3 CONDITIONAL COMPILATION
It is possible to compile a certain part of program (source code) conditionally. Certain pre-processor directives help us in this regard. One such directive is #ifdef. It stands for if defined.
A typical directive looks as follows.
#ifdef stdout
The syntax rules want the word #ifdef to start in first column. It is worth noting is that preprocessor directives are not format free. They do not use semicolon to terminate.
This pre-processor directive tests the symbol appearing next. If this symbol is defined at this stage, the code following this directive till directive #endif will be compiled.
Here the symbol is stdout. It is defined in header file stdio.h. If we have included this file in the program, then this symbol ...
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