Standard 'Hello World' Program

Presented below is a simple version of 'Hello World' that uses the Str class. Although not impressive, it is a good first step in getting comfortable with Str. Here is the C-style I/O version:

#include "Str.hpp"
#include <stdio.h>

int main(int argc, char* argv[]) {

    // Create a string on the Heap and print it

    Str s = "Hello World!";
    printf("s = %s\n", (const char*)s);
        
    // Set it equal to something and print it again

    s = "Goodbye!";
    printf("now s = %s\n", (const char*)s);

    return 0;
    
}

And here is the same version that uses C++-style I/O:

#include "Str.hpp"
#include <iostream>
using namespace std;

int main(int argc, char* argv[]) {

    // Create a string on the Heap and print it

    Str s = "Hello World!";
    cout << "s = " << s << endl;
        
    // Set it equal to something and print it again

    s = "Goodbye!";
    cout << "now s = " << s << endl;

    return 0;
    
}

Look at your favorite version and we'll review some concepts:

• In both programs, a string class 's' is created on stack.

• In both programs, 12 bytes of heap data are automatically allocated by 's' for the string data, and "Hello World!" plus a NULL is copied to this heap memory.

• The C-style program uses the (const char*) conversion feature of Str to give printf the char* type it can handle.

• The C++-style program uses the operator<< feature of Str to work nicely with cout

• In both cases, s = "Goodbye!" copies the char* string "Goodbye!" over top of "Hello World!".

• In both cases, the Str::~Str() destructor is automatically invoked when main() exits. This automatically frees the 12 bytes of heap data that was initially created.