Making a timer...

Hi, I wqas wondering, how exactly are timers made in C++, and how are they manipulated so that they restart after a certain amount of time...

I hope some1 out there can help...
:)

the only way I really know how depends on a CPU-intensive loop and I would never recommend it to anybody, but:

Code:

---

time_t begin,length,end;
begin=clock();
end=begin;
while(end-begin<length)
{
    end=clock();
}

---

then you take in length (milseconds?) from the user...

is that the only code thats needed, arent there any header files needed to make it work, or did u just not bother putting them in...

I didn't bother putting them in... you need <ctime>, and like I said, you need the user to put in the amount of time they want to wait... or have it passed in somehow... but here's another link to help you out if you want to go that way...

http://cppreference.com/stddate.html

there are also some non-standard methods to actually put your program's thread into a sleep (look around for sleep()), but like I said, they're non-standard. the pro to those is that they don't eat up cpu cycles...

Thank u, all i need to do now is to get use to the using the time functions, and I should be able to put it in when ever I like, cheers for the help...

:)

np... but use it sparingly, because like I said it's very CPU intensive... and as a side note, it makes for a good function...

There is more information in the Programming FAQ.

If you're using Windows, be aware that the time can be inaccruate when timing milliseconds. The results are returned with millisecond precision, but the variables are updated only (about) every 50 milliseconds. And with multitasking, the timing can be off even more.

k, ill keep that in mind when I make my programs, by the way, do u have any ideas on how to make the clock start on the user's input, not when the program starts. I tried this code below, but it didn't work, any ideas???

(The program is just an example)

Code:

---

#include <iostream>
#include <stdlib.h>
#include <time.h>

using namespace std;

int main(int argc, char *argv[])
{
    int num;
   
    cout << "Please press '1' to start the clock" << endl;
    cin >> num;
    if(num == 1)
    {
    while(num = 2)
    {
    time_t begin,length,end;
    begin=clock();
    end=begin;
    cout << clock() << endl;
    }
    }
    else
    {
        cout << "Please press '1'" << endl;
        int main();
    }
    system("Pause");
    return 0;
}

---

You might want to check your program logic. Specifically, that while loop looks a little out of place.

I admit, it is a bit shabby, but it was rushed and my compiler doesn't pick a fight with it, so for now its ok... but how can I make the timer start on the user's input, and not when the program starts. Also, is there a way to get the computer to read off the clock so that when it gets to a certain value, it outputs something, because I was thinking of having it output random strings after a random number of seconds...

I a tad stuck rite now, help would be greatly valued...

:)

cout << "enter whatever" << endl;
cin >> whatever;
//get current time here---call it startTimer
//do something here
//get current time here---call it stopTimer
//subtract startTimer from stopTimer
//see if difference between the two exceeds your time limit or do whatever else you want with it.

no, you can't have the user start the clock... the clock() function by definition returns how long the program's been running - you just have to pick up the start time and monitor the end time until the difference is the amount of time you wanted to wait...

The function clock() returns a clock_t type, not time_t. This code will only both clock_t and time_t are typedef'd to the same type.

you're right, but in this case it really doesn't matter all that much... you could use an unsigned int and get the same result...

I think time_t may be defined as a struct, in which case the code would not work. Although time_t is usually nothing more than the number of seconds since 1978(or some date like that), after 2030, or so, the number of seconds will overflow. Hence when determining the number of seconds between two time_t's, use one of the special purpose functions designed for this, such as difftime

Checked and found that time_T pretty much has to be an integer. Most implementations will overrflow in the year 2038, henceforth the type will most likely be 64-bit.

Heh. The year 2038 bug.

I would have thought they'd modify the start date for the clock mechanism to a newer date. Or better yet make a preprocessor that adds the current date when it compiles the compiler.

Also if you dont mind windows specific code you can look up QueryPerformanceCounter and QueryPerformanceFrequency.

>Checked and found that time_T pretty much has to be an integer.
No, it doesn't. time_t can be a floating point type just as easily as a signed or unsigned integral type. The size and representation are completely up to the implementation, so you cannot assume anything more than the fact that time_t is arithmetic, and can be used to compare with (time_t)-1. Everything else is non-portable.

unless you wanted it to be syncronized while the computers shut down or the same as the computer clock you can do this

Code:

---

#include <iostream.h>
#include <windows.h>
int main()
{
int loop; // in case you wanted it to do something over and over
for (loop=0;loop>=0;loop++)
{
Sleep(60000); // a minute, one second is 1000, do the math
cout << "\a";
}

return 0;
}

---

almost positive i didn't make any mistakes-i hope

Quote:

---

Originally Posted by killdragon

unless you wanted it to be syncronized while the computers shut down or the same as the computer clock you can do this

Code:

---

#include <iostream.h>
#include <windows.h>
int main()
{
int loop; // in case you wanted it to do something over and over
for (loop=0;loop>=0;loop++)
{
Sleep(60000); // a minute, one second is 1000, do the math
cout << "\a";
}

return 0;
}

---

almost positive i didn't make any mistakes-i hope

---

a few, actually... here's what the code should look like:

Code:

---

#include <iostream> //<iostream.h> is depreciated
#include <windows.h> //not too sure about this one

int main()
{
  //for (int loop=0;loop>=0;loop++) //infinite loop - might as well declare loop here
          //because it most likely won't be used outside the
          //scope of the loop

  for(;;)  //does the same as above, but saves a teeny bit of memory
  {
    Sleep(60000); //inadvisable - not portable, but it does free up the CPU
    cout << "\a";  //ringing the system bell every minute...
  }

return 0;
}

---

>//<iostream.h> is depreciated
Deprecated means that something is still standard but not assured to be in the next revision. iostream.h is not a part of the C++ standard at all, deprecated or not. So while an implementation is allowed to give you iostream.h according to the rules of implementation-dependent extensions, the standard makes no guarantees as to its contents. I could legally write a compiler that supports iostream.h and leave it empty. ;)

>//not too sure about this one
It should exist on a Windows box, otherwise I wouldn't hold my breath.