text: In this C++ tutorial, let us have a look at preprocessors, types and sample program for better understanding the concepts.
  Introduction of Preprocessor
  Preprocessors are the directives which tell the compiler to preprocess the source code before compilation begins. All of these preprocessor directives begin with a ‘#’ (hash) symbol and it is placed at the beginning of a statement in a C/C++ program.
  Some examples: #include, #define, #ifndef etc.
  Types of Preprocessor
  The different types of preprocessor directives are:
  - Macros
  - File Inclusion
  - Conditional Compilation
  Macros
  Macros are a part of code in a program which is given some name. Whenever this name is found by the compiler, it replaces the name with the actual piece of code. The #define directive is used to define a macro.
  Program for macros
  #include <iostream> // macro definition #define LIMIT 5 int main() { for (int i = 0; i < LIMIT; i++) { std::cout << i << "\n"; } return 0; }
  Output
  0 1 2 3 4
  File Inclusion
  This type of preprocessor directive tells the compiler to include a file in the source code program.
  It is of two types:
  Header File or Standard files
  The header files include the definition of pre-defined functions like cin, cout, etc. These files must be included for working with desired functions.
  Syntax
  #include< file_name >
  user-defined files
  When a program becomes very comprehensive, it is a good method to divide it into smaller files and include whenever required. These types of files are called user-defined files.
  Syntax
  #include"filename"
  Conditional Compilation
  Conditional Compilation directives are a kind of directives that helps to compile a specific part of the program based on some conditions. This can be done with the help of two preprocessing commands such as ‘ifdef‘ and ‘endif‘
  Syntax
  #ifdef macro_name statement1; statement2; statement3; . . . statementN; #endif