Abstract classes and class organization in C++ - c++

Question

I would like to create a basic abstract class in C++, where the subclasses are each in a separate file. My abstract class looks something like
class Process_Base{
public:
virtual void process() = 0;
}
Should a simple implementation like this be contained entirely in a header file? If it is do I need to have a .cpp file associated with it?
When I create the subclasses what should their header file look? I was thinking .cpp file for the subclass should look something like
#include "Process_Base.h"
class Hello_Process : public Process_Base{
void process(){
printf("%s\n", "Hello, World");
}
}
Could someone verify that I am approaching this correctly, and if not give a simple example of what I should be doing.
UPDATE
I continued with the implementation but I am now getting the following compiler error
g++ -c -Wall -g Process_Message.cpp
Process_Message.cpp:4: error: expected class-name before ‘{’ token
The following is the abstract class header
// Abstract header .hpp file
class Process_Base{
public:
virtual void process() = 0;
};
the subclass header
// The subclass header .hpp file
#include "Process_Base.hpp"
class Process_Message : public Process_Base {
public:
void process();
};
and the implementation
// Simple implementation .cpp file
#include <stdio.h>
#include <string.h>
class Process_Message : Process_Base {
public:
void process(){
printf("%s", "Hello");
}
}
I don't understand why I am getting the error, can someone please explain.

Answer 1

You're missing ; at the end of Process_Base declaration, when you include the file, the compiler goes nut. correct is:
class Process_Base{
public:
virtual void process() = 0;
};

Answer 2

Why this 'Process_Base' is there in below code? You have already mentioned inheritance in header file,right?
// Simple implementation .cpp file
#include <stdio.h>
#include <string.h>
class Process_Message : Process_Base {
public:
void process(){
printf("%s", "Hello");
}
}
Also don't forget to type ';' at the end of the class declaration after '}'

Answer 3

Your correct code should look like this:
//Process_Message.h
#include "Process_Base.hpp"
class Process_Message : public Process_Base {
public:
void process();
};
//Process_Message.cpp
#include <stdio.h>
#include <string.h>
#include "Process_Message.h"
void Process_Message::process()
{
printf("%s", "Hello");
}

Answer 4

Don't forget to declare your overrides as virtual, or they will hide parent methods instead of implementing them.
#include <iostream>
class Process_Base
{
public:
virtual ~Process_Base() {}
virtual void process() =0;
};
class Process_Message : public Process_Base
{
public:
virtual void process(); // <- virtual
};
void Process_Message::process()
{
std::cout << "Hello";
}
The above should compile fine