WEBVTT 00:00.430 --> 00:07.990 Now let's embark on the compilation process, which begins with a set of source files that you intend 00:07.990 --> 00:09.040 to compile. 00:09.040 --> 00:14.680 So while it is possible to have just one source files, larger programs typically consist of multiple 00:14.680 --> 00:15.220 files. 00:15.220 --> 00:21.340 So this approach not only facilitates project management but also accelerates compilation. 00:21.340 --> 00:27.400 So if a single file undergoes changes, you only need to recompile that specific file instead of the 00:27.400 --> 00:28.780 entire code base. 00:28.780 --> 00:35.530 So this C source file contains macros indicated by hashtag define. 00:35.680 --> 00:43.420 Now we will create open the notepad here and we will create some define here. 00:43.420 --> 00:46.180 So this is the C file. 00:46.940 --> 00:56.030 Macro here, so we will save it as a C main dot, my app dot C and here, as you can see here, Mousepad 00:56.060 --> 01:04.250 indicated that this is something that has macro and write it it on color font. 01:04.250 --> 01:07.670 So and we also have the include here. 01:07.670 --> 01:17.630 So the include directive here are used to incorporate header files with dot h extensions that the source 01:17.630 --> 01:18.590 files relies on. 01:18.590 --> 01:26.810 So during the preprocessing phase, these derivatives are expanded resulting in pure C that is ready 01:26.810 --> 01:28.040 for compilation. 01:28.040 --> 01:36.170 So to illustrate this process, let's examine an example application using the g c c compiler, which 01:36.170 --> 01:42.830 serves as a default compiler in many Linux distributions and including Ubuntu. 01:42.860 --> 01:45.650 The operating system installed on um. 01:45.650 --> 01:53.180 Uh, more that like the most popular operating system in Linux, but in Linux you will also get that 01:53.180 --> 01:54.920 GCC compiler here. 01:54.920 --> 02:01.910 So it's important to keep in mind that the results obtained from other compilers like Clang or Visual 02:01.910 --> 02:03.800 Studio will be similar. 02:03.800 --> 02:13.430 As I mentioned earlier, I'll code examples in this course will be compiled into 8664 code unless specified 02:13.430 --> 02:14.000 otherwise. 02:14.000 --> 02:16.490 So now we will. 02:17.430 --> 02:18.990 Chris Scott. 02:20.470 --> 02:29.800 And which firstly we will include the include the studio hatch because we will need that for print here. 02:29.800 --> 02:32.590 And after that we will define. 02:33.870 --> 02:34.770 Define. 02:35.740 --> 02:37.120 Format string. 02:37.690 --> 02:41.050 And this format string is going to be s, as you know. 02:41.620 --> 02:43.390 And we will also define. 02:44.510 --> 02:45.950 Define message. 02:47.000 --> 02:48.020 And it's going to be. 02:48.020 --> 02:48.830 Hello. 02:51.150 --> 02:52.650 Hello, world. 02:56.990 --> 03:00.710 And after that we will create integer Main here. 03:00.830 --> 03:03.740 And this integer XY here. 03:04.220 --> 03:07.730 Character Visualz here. 03:09.110 --> 03:12.770 And after that we will print use the print function. 03:14.740 --> 03:15.290 Printf. 03:15.460 --> 03:16.180 Here. 03:16.210 --> 03:18.430 First we will pass the format string. 03:19.460 --> 03:25.040 And after that we will pass the message, which is Hello, world traditional message here. 03:25.040 --> 03:27.680 And after that we will return zero. 03:28.490 --> 03:31.430 Let's close the braces here. 03:34.090 --> 03:34.930 That's it. 03:35.470 --> 03:43.540 And in a moment here, you will see what happens with this file in the rest of the compilation process. 03:43.540 --> 03:47.260 But for now, we will just consider the output of the preprocessing stage. 03:47.260 --> 03:54.760 So by default, GCC will automatically execute all compilation phases, so you have to explicitly tell 03:54.760 --> 04:01.440 it to stop after preprocessing and to show you intermediate output. 04:01.450 --> 04:01.770 Right. 04:02.100 --> 04:05.830 We will tell the GCC that and. 04:07.050 --> 04:08.970 Here for GCSE. 04:09.000 --> 04:12.780 This can be done using the common GCSE. 04:13.200 --> 04:14.220 Let's clear here. 04:14.220 --> 04:19.680 So gcse uppercase e parameter and p parameter. 04:19.680 --> 04:31.710 So where e here tells GCSE to stop after pre-processing and P here causes the compiler to omit the debugging 04:31.710 --> 04:34.860 information so that the output is a bit cleaner. 04:34.860 --> 04:35.250 Right. 04:35.250 --> 04:38.310 So here we will write GCC. 04:39.850 --> 04:46.450 E p And after that we all sorry, we need to go to desktop because we saved this file in desktop. 04:46.450 --> 04:50.230 And here let's LZ Oops. 04:52.500 --> 04:55.020 Let's save it on desktop here. 04:59.630 --> 05:00.830 And here. 05:01.770 --> 05:15.450 Here we have my apk and clear so gcc e p and after that we will pass our file which is named my APK. 05:16.580 --> 05:18.040 My apps. 05:18.440 --> 05:20.050 And here it is. 05:20.060 --> 05:20.960 So. 05:23.190 --> 05:26.920 This is preprocessing phase here and we have this information. 05:26.940 --> 05:36.060 So the studio dot h heater is included, included in this entirety with all of its type definitions, 05:36.060 --> 05:42.620 global variables and functions, prototypes copied in to the source files. 05:42.630 --> 05:49.920 So because this happens for every include directory directory here directive and let's actually copy 05:49.920 --> 05:50.430 that. 05:55.510 --> 06:00.610 And we will copy that right now and we will paste and analyze it further. 06:04.220 --> 06:04.850 New. 06:04.850 --> 06:06.020 And that's it. 06:10.430 --> 06:12.800 And here we have integer Main here. 06:12.800 --> 06:13.610 So. 06:15.080 --> 06:23.330 And the preprocessor also really expands our use of any macros you define using, define. 06:23.330 --> 06:30.590 And in this example, this means both arguments here, the format string and here the format string 06:30.590 --> 06:38.810 and message are evaluated and replaced by the constant strings that they represent here. 06:38.960 --> 06:44.750 But strangely, we don't have the format string format, string. 06:44.750 --> 06:46.760 So we have this one. 06:49.610 --> 06:51.920 Mistyped this string here. 06:52.010 --> 07:01.700 And if you try to do that, like generally usually compile this my apk, we will get an error here because 07:01.700 --> 07:07.310 we have this string not defined properly because of the. 07:09.440 --> 07:10.100 Vermis. 07:12.050 --> 07:12.950 Yeah, that's it. 07:12.950 --> 07:16.280 And now if we compile this, this will compile without problem. 07:16.280 --> 07:18.550 And let's run this again. 07:18.560 --> 07:22.890 And here, as you can see, here we are seeing s and hello world here. 07:26.040 --> 07:26.910 Now, let's. 07:30.220 --> 07:32.020 And as you can see here. 07:33.250 --> 07:38.830 This means that both arguments to printf which is. 07:39.510 --> 07:48.910 Format, string and message are evaluated and replaced by the constant strings that they represent. 07:48.930 --> 07:56.820 So this was the preprocessing phase of C and compiled languages. 07:56.820 --> 08:00.090 And in next lecture we will also learn the compilation phase. 08:00.090 --> 08:02.130 So I'm awaiting you in the next lecture.