MakeFile in C++ and its applications

Given a C++ program, the task is to break the entire program in the form of Makefile. It is basically used to create .cpp file and .h file for each class/function and its functionalities and later link them all through a Makefile command available in C++.

Advantages:

• It makes codes more concise and clear to read and debug.
• No need to compile an entire program every time whenever you make a change to a functionality or a class. Makefile will automatically compile only those files where change has occurred.
• Generally, in long codes or projects, Makefile is widely used in order to present projects in more systematic and efficient way.

Example: Create a program to find the factorial and multiplication of numbers and print it.

Traditional Way

CPP

// Program to calculate factorial and
// multiplication of two numbers.
#include <bits/stdc++.h>
using namespace std;

// Function to find factorial
int factorial(int n)
{
    if (n == 1)
        return 1;
    // Recursive Function to find
    // factorial
    return n * factorial(n - 1);
}

// Function to multiply two numbers
int multiply(int a, int b) { return a * b; }

// Function to print
void print() { cout << "makefile" << endl; }

// Driver code
int main()
{
    int a = 1;
    int b = 2;
    cout << multiply(a, b) << endl;
    int fact = 5;
    cout << factorial(5) << endl;
    print();
    return 0;
}

Output

2
120
makefile

Use Makefile to run the above program:

• File Name: main.cpp

CPP

#include <bits/stdc++.h>

// Note function.h which has all functions
// definitions has been included
#include "function.h"

using namespace std;

// Main program
int main()
{
    int num1 = 1;
    int num2 = 2;
    cout << multiply(num1, num2) << endl;
    int num3 = 5;
    cout << factorial(num3) << endl;
    print();
}

• File Name: print.cpp

CPP

#include <bits/stdc++.h>

// Definition of print function is
// present in function.h file
#include "function.h"
using namespace std;

void print() { cout < "makefile" << endl; }

• File Name: factorial.cpp

CPP

#include <bits/stdc++.h>

// Definition of factorial function
// is present in function.h file
#include "function.h"
using namespace std;

// Recursive factorial program
int factorial(int n)
{
    if (n == 1)
        return 1;
    return n * factorial(n - 1);
}

• File Name: multiply.cpp

CPP

#include <bits/stdc++.h>

// Definition of multiply function
// is present in function.h file
#include "function.h"
using namespace std;

int multiply(int a, int b) { return a * b; }

• File Name: function.h

CPP

#ifndef FUNCTION_H
#define FUNCTION_H

void print();
int factorial(int);
int multiply(int, int);

#endif

Commands to Compile and Run the above program:

Open Terminal and type commands:
g++ -c main.cpp
g++ -c print.cpp
g++ -c factorial.cpp
g++ -c multiply.cpp
g++ -o main main.o print.o factorial.o multiply.o
./main

Note: g++ -c filename.cpp is used to create object file.