What’s a header? What’s a source-code file? Discuss the purpose of each.?

I assume C++. This is what I understand:

Header files are used to declare things:

class Bob

{

int data;

public:

Bob();

~Bob();

void Test();

};

Source files are used to define things:

#include "Bob.h"

Bob::Bob()

{

data = 2;

{

Bob::~Bob()

{

//do something

}

The reason why this done, instead of just putting it all the code in one file is because: Usually, if you were to change some of the code in this class, then all files that include that class would need to be rebuilt. This can be very annoying with projects that have 400+ files, where a lot of them include that class, because the compile time could become exceedingly long for even the smallest changes.

But, when you separate the files into header files and source files then the files that include that data will only need to be rebuilt if you change the header. Changing the source file means that only that one file will need to be rebuilt.

On a side not, you will probably want to put some header guards in there too, so there are no "class type redefinition" errors.

class Bob; // makes all other files aware of Bob

#ifndef BOB

#define BOB // prevents Bob from being defined multiple times

class Bob // defines Bob

{

int data;

public:

Bob();

~Bob();

void Test();

};

#endif