An Initial Example

This is a simple variation of the common "Hello World" program. It is one of the simplest, yet complete, C++ programs:

#include <iostream>

using std::cout;
using std::endl;

int main(int argc, char *argv[])
{
    cout << "Welcome to the Crawford Group!" << endl;

    return 0;
}

Open a new c++ source file called welcome.cc in your favorite editor and put the above code inside. Then we must compile the source:

c++ -c welcome.cc
c++ welcome.o -o welcome

The first command will generate an object file, welcome.o, while the second will generate the actual executable program, welcome. You can execute the final program from the command line:

$ ./welcome
Welcome to the Crawford Group!
$

The lines that begin with using … in the source file allow you to use the functions std::cout and std::endl without typing the prefix std:: every time. The signature std:: indicates that these functions belong to the namespace called std. Namespaces allow you to have functions that may be called the same thing, without confusing which one is to be used. Declaring using std::cout; at the start of the program indicates to the complier that when we type cout we really mean std::cout.