Can goto() statements be avoided in this program -- pls place code?

Projects Programming
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GolamMostafa:
as I have not called upon any subroutine..

I'm not sure the term "subroutine" really applies in C++. loop() is a function. loop() is called by the main() function, which is hidden in the Arduino core library but I know you are aware of it from our previous discussion of serialEvent(). So if the term did apply then loop() would be a subroutine.

GolamMostafa:
justifying the use of return statement when I am already in a routine -- the loop().

Let's dig out our old friend main():

int main(void)
{
 init();

 initVariant();

#if defined(USBCON)
 USBDevice.attach();
#endif
 
 setup();
    
 for (;;) {
 loop();
 if (serialEventRun) serialEventRun();
 }
        
 return 0;
}

So when you use the return statement in loop() it returns to main(), does the stupid serialEventRun() thing, then starts the next for loop, which calls loop() again. That takes you back to the top of the loop function.

GolamMostafa:
What would happen if I would use exit()

You exit the program. Since there is nowhere to exit to on your microcontroller everything just hangs after that. Give it a try.

GolamMostafa:
or break;.

break is for use in for, while, or do…while loop or switch...case so you would get a compiler error "error: break statement not within loop or switch".