Chapter 8 // Drill 1 - Principles & Practice Using C++

In this exercise I am using Visual Studio Community 2017 and the header file "std_lib_facilities.h" which can be found here:

http://www.stroustrup.com/Programming/PPP2code/std_lib_facilities.h

Chapter 8 // Drill 1

1. Create three files: my.h, my.cpp, and use.cpp. The header file my.h contains:

extern int foo;

void print_foo();

void print(int);

The source code file, my.cpp #includes my.h and std_lib_facilities.h, defines print_foo() to print the value of foo using cout, and print(int i) to print the value of i using cout.

The source code file use.cpp #includes my.h, defines main() to set the value of foo to 7 and print it using print_foo(), and to print the value of 99 using print(). Note that use.cpp does not #include std_lib_facilities.h as it doesn't directly use any those facilities.

Get these files compiled and run. On Windows, you need to have both use.cpp and my.cpp in a project and use { char cc; cin >> cc} in use.cpp to be able to see your output. Hint: You need to #include <iostream> to use cin.

//my.h

#pragma once
//my.h

//declarations
extern int foo;
void print_foo();
void print(int);

void keepWindowOpen();

//my.cpp

//my.cpp

#include "my.h"
#include "std_lib_facilities.h"

int foo;

//print the value of foo
void print_foo()
{
 cout << foo << endl;
}

//print a given integer
void print(int i)
{
 cout << i << endl;
}

//function to keep the window open
void keepWindowOpen()
{
 char c;
 cout << "\nPress any key to quit: ";
 cin >> c;
}

//use.cpp

//use.cpp

#include "my.h"

int main()
{
 //assign 7 to foo
 foo = 7;

 //print what's in foo
 print_foo();

 //send an integer to be printed to screen
 print(99);

 //keep window open until any key press
 keepWindowOpen();
}

A pretty simple exercise which showcases how to split a project up into separate files. Seeing as how you can't use keep_window_open() from std_lib_facilities I created a function in my.cpp which does the same thing and then declared it in my.h so it could be used in main(). This way I didn't have to #include <iostream> in use.cpp as it was already declared in my.cpp from the other header file.