Create stopwatch with C++

C++ is a great language but to make something using it is a bit difficult. But that doesn't mean you can't do anything with it. You can create small console based applications and that's what we are going to do. I will show you how to create a simple stopwatch with C++.

I got this idea from my javascript stopwatch project and thought how can I create something like that in C++. So let's see how to do it !!

Requirements

• C++ compiler (or you can use any online platform. My recommendation is: Repl.it)
• Text editor
• Some knowledge of C++

Step 1: Write the base code

We will start by writing the base code for our console application.

• Create a folder and give it a name. e.g. cpp-stopwatch
• Create a file named stopwatch.cpp in that folder.

// stopwatch.cpp
#include <iostream>

using namespace std;

int main() {
   cout << "stopwatch" << endl;
}

• To compile and run this code, open your terminal or command prompt and navigate to that folder and run the following commands

# compile
g++ stopwatch.cpp -o stopwatch

# run 
./stopwatch

Use these commands every time you make changes to your C++ file.

Step 2: Displaying our stopwatch

First we will start by displaying our stopwatch in console before adding functionality to it. For that we will create necessary variables and a function named displayTime to display our stopwatch.

// stopwatch.cpp
#include <iostream>

using namespace std;

void displayTime(int hours, int minutes, int seconds) {
   cout << hours << ":"
        << minutes << ":"
        << seconds << endl;
}

int main() {
   int hour = 0;
   int min = 0;
   int sec = 0;

   displayTime(hour, min, sec);

}

Step 3: Stopwatch functionality !!

Now the interesting part, functioning of stopwatch. If you are familiar with javascript, you already know that there is a built-in function setInterval that runs the code after the specified interval. But how can we do that thing in C++ ??

In C++ we can use a function called sleep which is available in the header unistd.h in linux and windows.h in windows.

Sleep function takes number of seconds and stops the code for the specified duration.

#include <iostream>
#include <unistd.h> // in linux: sleep()

// #include <windows.h> // in windows: Sleep()

using namespace std;

int main() {
   cout << "wait for 5 seconds !" << endl;
   sleep(5);
   cout << "5 seconds passed away !" << endl;
}

So, we have a way to stop our code but we need a way to increment number of seconds continuously. For that we will use LOOOOOP.

#include <iostream>
#include <unistd.h> // in linux: sleep()

// #include <windows.h> // in windows: Sleep()


using namespace std;

int main() {
   int hour = 0;
   int min = 0;
   int sec = 0;

   // run the stopwatch continuously
   while(true) {
      sleep(1);
      sec++;

      cout << sec << endl;
   }  
}

Let's add the code for hours and minutes as well and also use our display function

#include <iostream>
#include <unistd.h> // in linux: sleep()

// #include <windows.h> // in windows: Sleep()


using namespace std;


void displayTime(int hours, int minutes, int seconds) {
   cout << hours << ":"
        << minutes << ":"
        << seconds << endl;
}

int main() {
  int hour = 0;
  int min = 0;
  int sec = 0;

  while(true) {
    sleep(1);

    sec++;

    if(sec > 59) {
      min++;
      sec = 0;
    } 

    if(min > 59) {
      hour++;
      sec = 0;
      min = 0;
    }

    displayTime(hour, min, sec);
  }
}

Running this code will start printing stopwatch with new time, line by line. We can handle this by simple clearing screen before displaying the next time.

• Add system("clear") in displayTime function
• We will also display initial time before entering the loop so that stopwatch display time from 0 hours, 0 minutes and 0 seconds instead of directly showing 1 second in console

#include <iostream>
#include <unistd.h> // in linux: sleep()

// #include <windows.h> // in windows: Sleep()


using namespace std;

void displayTime(int hours, int minutes, int seconds) {
   // for linux
   system("clear"); 

   // for windows
   // system("cls");

   cout << hours << ":"
        << minutes << ":"
        << seconds << endl;
}

int main() {
  int hour = 0;
  int min = 0;
  int sec = 0;

  displayTime(hour, min, sec);

  while(true) {
    sleep(1);

    sec++;

    if(sec > 59) {
      min++;
      sec = 0;
    } 

    if(min > 59) {
      hour++;
      sec = 0;
      min = 0;
    }

    displayTime(hour, min, sec);
  }
}

Finally, compile and run it and hopefully you will see your very own console stopwatch. To stop the stopwatch, use Ctrl + C

This one was beginner friendly and doesn't use threads and chrono library. You can find the source code and working example in my repl.

I am not an expert in C++ but trying new things and applying them is important. Hope you learned something new out of this simple C++ stopwatch project.