What does include iostream do

Question

As I started learning basic C    I ve always used the headings    include  lt iostream gt  using namespace std    I want to question what is the point of iostream  Is it required every time as a heading

User · Answer

indicates that the following line is a preprocessor directive and should be processed by the preprocessor before compilation by the compiler    So   include is a preprocessor directive that tells the preprocessor to include header files in the program     lt   gt  indicate the start and end of the file name to be included    iostream is a header file that contains functions for input output operations  cin and cout     Now to sum it up C   to English translation of the command   include  lt iostream gt  is    Dear preprocessor  please include all the contents of the header file iostream at the very beginning of this program before compiler starts the actual compilation of the code

User · Answer

That is a C   standard library header file for input output streams  It includes functionality to read and write from streams  You only need to include it if you wish to use streams

User · Answer

In order to read or write to the standard input output streams you need to include it   int main  int argc  char   argv           std  cout  lt  lt   Hello World    lt  lt  std  endl      return 0      That program will not compile unless you add  include  lt iostream gt   The second line isn t necessary  using namespace std    What that does is tell the compiler that symbol names defined in the std namespace are to be brought into your program s scope  so you can omit the namespace qualifier  and write for example   include  lt iostream gt  using namespace std  int main  int argc  char   argv           cout  lt  lt   Hello World    lt  lt  endl      return 0      Notice you no longer need to refer to the output stream with the fully qualified name std  cout and can use the shorter name cout   I personally don t like bringing in all symbols in the namespace of a header file    I ll individually select the symbols I want to be shorter    so I would do this    include  lt iostream gt  using std  cout  using std  endl   int main  int argc  char   argv           cout  lt  lt   Hello World    lt  lt  endl      return 0      But that is a matter of personal preference

[c++] What does "#include <iostream>" do?

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