WEBVTT 00:05.190 --> 00:10.980 So the third function callback is nothing, but it is a function which the new thread will going to 00:10.980 --> 00:11.960 execute. 00:11.970 --> 00:18.420 Write Such type of functions have a fixed prototype and the prototype should be should be that that 00:18.420 --> 00:20.490 these function must return void star. 00:20.490 --> 00:24.360 And the argument to this function is also void star, right? 00:24.360 --> 00:30.030 So you can see that the prototype of thread function callbacks is very generic, right? 00:30.360 --> 00:35.640 So as soon as the child thread starts, the child thread invokes this function, right? 00:35.640 --> 00:41.010 So in other words, this function will be executed in the context of a child thread, right? 00:41.550 --> 00:44.600 Now our new thread must do some useful work. 00:44.610 --> 00:48.130 Or maybe not useful, but a new thread must do some work. 00:48.150 --> 00:49.590 So what are we going to do? 00:49.590 --> 00:54.910 Is that I will simply extract the argument which was passed to our new thread. 00:54.930 --> 00:56.970 So what was the argument which was passed? 00:56.970 --> 01:01.050 The argument was nothing but the address of this input string. 01:01.050 --> 01:01.680 Right? 01:01.680 --> 01:07.830 So whatever memory you passed as the last argument to the P thread create function, the address of 01:07.860 --> 01:12.060 that memory will be available as an argument to this thread function callback. 01:12.060 --> 01:12.690 Right. 01:12.690 --> 01:15.540 So you simply type cast it into the car star. 01:15.540 --> 01:16.260 Right. 01:17.550 --> 01:23.910 And now what I will going to do is that I will going to create an infinite loop and inside that loop 01:23.910 --> 01:26.700 I will going to just print this string, right? 01:26.700 --> 01:33.060 And I will going to use sleep one so that our new thread take a rest of one second. 01:33.090 --> 01:38.370 Now in this Hello World program though, it is very simple and basic, but we will going to but we will 01:38.370 --> 01:41.680 going to discuss several basic points regarding Multithreading. 01:41.680 --> 01:45.100 Okay, so now let me compile this Hello World program. 01:45.100 --> 01:49.810 The instruction to compile a multi multithreaded program is written at the top of the file. 01:49.960 --> 01:55.720 So what you are going to do is that simply you can copy paste these lines, right? 01:56.470 --> 02:03.690 And note that for a multithreaded program you need to link your executable with the P thread library. 02:03.700 --> 02:08.800 So to specify the P thread library, you can simply write minus P thread. 02:08.800 --> 02:09.580 Right? 02:09.580 --> 02:17.350 And if you just press enter the hello world executable will be created and the expectation is that that 02:17.350 --> 02:25.870 the main thread should get paused right here and the child thread must run in this infinite loop. 02:25.870 --> 02:32.080 And every time the child thread must print this input string so you can see the same thing is happening 02:32.080 --> 02:32.770 right? 02:35.680 --> 02:41.530 So the child thread is running and it is printing the input string after every one second on the screen. 02:41.530 --> 02:47.920 In other words, the child thread is doing its job, whereas the main thread is halt at the line number 02:47.920 --> 02:48.960 77. 02:48.970 --> 02:49.690 Right. 02:51.940 --> 03:00.250 If we remove this line number 77 and if you execute this program again after compiling, of course, 03:01.180 --> 03:05.170 then you will see that nothing happens, right? 03:05.260 --> 03:12.820 Even before your child thread took a birth and start its life, your main thread had terminated and 03:12.820 --> 03:17.920 if your main thread terminates, then all the child threads in the program gets terminated automatically. 03:17.920 --> 03:18.580 Right? 03:19.450 --> 03:25.390 So in other words, by removing this pause call from the function, we have hardly given any chance 03:25.390 --> 03:29.080 to the child thread to take a birth and live its life. 03:29.350 --> 03:35.260 I will show you shortly in this section that how you can allow your main thread to terminate while having 03:35.360 --> 03:37.370 your child thread alive. 03:37.490 --> 03:44.030 So now we will go into analyze this Hello World Multithreaded program from various aspects and understand 03:44.030 --> 03:48.380 certain points regarding multithreading in the next couple of lecture videos.