Fundamental

Hello, World!

See the very first C++ Code:

#include <iostream>  // import header file(s)
using namespace std;  // invoke and specify the namespace
int main() {                // define main function
    cout << "Hello, world!";  // print Hello, world!
    return 0;                 // return 0，end main function
}

Run it with:

g++ -o hello hello.cpp

Here is the Java code as a comparison:

import some.java.packages;  // import declaration(s)
public HelloWorld {
    // the main method returns void and gets the argument 
    // args(String) for receiving CLI args
    public static void main(String[] args) {  
        System.out.println("Hello. World");
        // void return
    }
}

The package that is imported in Java is called the header file in C++. The same as Java, Header files in C++ can be user-created or system built-in. Besides, C++ has a concept called namespace. What is that?

Returning and Printing

Topics: Function call and return, return types

Below is a series of four printLyrics_v# functions, each of which has a blank where the return type should be. For each function, determine

• what the return type of the function should be,

• what value, if any, is returned, and

• what output, if any, will be produced if that function is called.

Is it appropriate for each of these functions to be named printLyrics? Why or why not?

_____ printLyrics_v1() {
    cout << "Havana ooh na na" << endl;
}
_____ printLyrics_v2() {
    return "Havana ooh na na";
}
_____ printLyrics_v3() {
    return "H";
}
_____ printLyrics_v4() {
    return 'H';
}

void printLyrics_v1() {
    cout << "Havana ooh na na" << endl;
}

string printLyrics_v2() {
    return "Havana ooh na na";
}

string printLyrics_v3() {
    return "H";
}

char printLyrics_v4() {
    return 'H';
}

Of these four functions, only printLyrics_v1 will print anything. Specifically, it prints out the string "Havana ooh na na.". The name “printLyrics” is inappropriate for the other functions, as those functions don’t actually print anything. 😃

The function printLyrics_v1 doesn’t return anything – it just sends information to the console. As a result, its return type should be void. The functions printLyrics_v2 and printLyrics_v3 each return string, since C++ treats anything in double-quotes as a string. Finally, printLyrics_v4returns a char, since C++ treats anything in single quotes as a character.