Structure of a C++ program

Example.

/***********************************************
* Name:       helloworld.cxx
* Author:     Leo Liberti
* Source:     GNU C++
* Purpose:    hello world program
* Build:      c++ -o helloworld helloworld.cxx
* History:    060818 work started
***********************************************/

#include<iostream> 

int main(int argc, char** argv) {
  using namespace std;
  cout << "Hello World" << endl;
  return 0; 
} 

• Each executable program coded in C++ must have one function called main()
  int main(int argc, char** argv);
• The main function is the entry point for the program
• It returns an integer exit code which can be read by the shell
• The integer argc contains the number of arguments on the command line
• The array of character arrays **argv contains the arguments: the command ./mycode arg1 arg2 gives rise to the following storage:
  argv[0] is a char pointer to the string ./mycode
  argv[1] is a char pointer to the string arg1
  argv[2] is a char pointer to the string arg2
  argc is an int variable containing the value 3

• C++ programs are stored in one or more text files
• Source files: contain the C++ code, extension .cxx
• Header files: contain the declarations which may be common to more source files, extension .h
• Source files are compiled
• Header files are included from the source files using the preprocessor directive #include
  #include<standardIncludeHeader> #include "userDefinedIncludeFile.h"