Oh, now i get it. Thank you. I will add that change in to my code.

but system("pause"); is bit more time consuming right? like for every number there is a system("pause"); will take more time then just printing the list, then letting the user decide when he wants to pause the list and continue by the kbhit() right? Correct me if i am wrong.

The Sleep(75);, is required because it is in the series mode. if the user input some 100 numbers of the series, for example 400, that function prints the numbers from the start, so by using sleep for that mode, it it more nice to see the whole series rather than the series being printed out instantly. Moreover, if it is printed instantly, the user will need to scroll up a lot to see smaller numbers of the series. Then the use of kbhit(), goto will have no use also

@ReinstateMonica Yea, i figured out a way to avoid the problem that is caused by the series, if it runs for a long time. i used %.3g instead of %lf so its kinda working fine now.

@Quuxplusone Hi sir, I have tried to improve from my past version; Are you able to rate it again? Sorry for bothering you too much though.

@ReinstateMonica Ouh, cause for school project, just for the content, i added it. will remove it. Thanks fro the suggestion. But the question is will unanswered though