C++: About Header

Consider the following codes

#include <iostream>
int main()
std::cout << "Welcome to C++!\n";
return 0; // indicate that program ended successfully

Inclusion of Header Files (#include)

The  line with  #include notation, allows the programmer to call the contents of one program within an another program. The C++  compiler enforces that all the objects are to be declared before use. The the include directives set a reference to the other program in the beginning of the code, and these programs or routines are processed before compiling the local code. Since, all these referred programs in directives are processed before the current code, these are known as Preprocessors or Macros.

Header Files:
  • Standard Template Library
    • Why ? Just like your face, header files carries all predefined conditions those are acceptable to the compiler. And looking at your face that is attached to a name, your friend will know who you are. This remain headers remain constant all along, but they are not supposed to replace constant data type.
  • Preprocessor or Macros
    • More defined designations before compiling

    • Meaning more elaborated and predefined conditions those should be checked out before  checking on the rest of the code in a function.


Standard Template Library

  • map
  • memory
  • new
  • numeric
  • ostream
  • queue
  • set
  • sstream
  • stack
  • stdexcept
  • streambuf
  • string
  • strstream
  • typeinfo
  • utility
  • valarray
  • vector
  • algorithm
  • bitset
  • complex
  • deque
  • exception
  • fstream
  • functional
  • iomanip
  • ios
  • iosfwd
  • iostream
  • istream
  • iterator
  • limits
  • list
  • locale
Preprocessors OR Macros: Preprocessor directives are used in the headers, and  are always preceded by a pound sign (#). The preprocessors are executed before the actual compilation of code initiates, some standard preprocessors are listed below

Preprocessors OR Macros

  • #define
  • #elif
  • #else
  • #endif
  • #error
  • #if
  • #ifdef
  • #ifndef
  • #include
  • #line
  • #pragma
  • #undef

C++ also includes the Standard C Library: These libraries are also preceded by #include directives.