If you have gone throughModule 1 and2, themain() function is needed for the execution point of C/C++ programs. That means compiler start the program execution at main() function. A complete story about the main() function is given inModule Y. In your C/C++ program also, there are other functions that you already familiar with such as printf(). You can see then, C/C++ programs just consist of functions with main() as the execution point.

1. Create a new empty Win32 console application project named mymain and add a C++ source file named mymainsrc as done in previous lab practice. Make sure you set this project to be compiled as C code. Type the following codes.

#include<stdio.h>

 

void main(void)

{ }

2.  Then add more codes. You can omit the comments.

#include<stdio.h>

// this '//' means line comment...will be ignored by compiler

// the first void means main() doesn't return anything

// the second void means, main() doesn't receive anything

void main(void)

// the beginning of the main/other function body is indicated by} – a curly brace

{

     // declare and initialize a variable with integer type...

      // every C/C++ statement will be terminated by ; (semi colon)

     int MyAge = 12;

     // printf() is another built-in/standard function for standard

     // output - your terminal/console/screen that defined in stdio.h.

     // In the following three printf()s, they receive and return

      // formatted strings...

     // the \n is an escape to new line...more on this later...

      printf("My name is Mr. C. Cplusplus\n");

      printf("Hello C/C++ world!\n");

      printf("-Learning about function-\n");

     // the following printf() return the age...

      printf("My age is %d\n", MyAge);

     // no return statement coz main() return nothing (void)

      // the end of the main()/other function’s body is indicated by }

}

3. Build and run your program. The output should be as shown.

4. In the program we define the main() function but what about printf()? The definition of the printf() is in stdio.h header file. That is why we need to include #include <stdio.h> in our program so that compiler know what the printf() is. We pass some string argument to printf() function and then it return the string to the screen – the standard output.

5. The #include is called preprocessor directive. In a simple word, we instruct a compiler to find stdio.h file and read/process it.

6. Why we do this? In the C/C++ programs, for commonly and frequently used routines such as printf(), no need for us to retype the code for printf() function’s definition, how it works, declaration etc., just include in our program using the #include preprocessor directive and it make our program smaller and structured or modular. Don’t forget also the printf() and other standard functions are reusable.

7. By using the #include directive, compiler know what file to find but how your compiler find these include files? During the installation, the include and library paths have been set in your environment variables. For Windows XP Pro example is shown on the right.

8. Then, how your compiler search those include (and other project related files) files if there are more than one include paths (for example if your machine has more than one version of the VC++)? The paths and sequence have been set in your project Options. Click Tools →Options menu.

9. Expand the Projects and Solutions folder and select VC++ Directories link. In the Show directories for: select Include files. The paths are given there. You can add (if you have third party, non standard or user-defined include files) or remove the not useable include files. Don’t forget to explore other options in the Options form but do not change any setting.

10. Finally, you can check the location/path of the include files physically and for stdio.h example is shown below for Visual C++ 2005 EE (version 8) and Visual Studio .Net 2003 (version 7) that were installed on Windows XP Pro.

11. You can also see that under the include folder, there are also header files without the .h extensions. Those header files used for C++ programs.

12. The file must be found and read before any function it defined can be used in our program including themain() and that is why it is put outside the main() body, at the beginning of the program. It is in global space so that any function that stdio.h defined such as printf() can be used anywhere in the program/file/source code or other file/source code that the main() program calls.

13. If you want to see those include files that are used during the building process, you can set the Show Includes option in the project setting.

14. Click the Project →your_project_name Properties menu. Select Advanced link under C/C++ sub folder. Change the Show Includes option to Yes (/showincludes) and click the Apply button. Close the property form and rebuild your program.

15. See messages in the Output window. It should be as shown below. Not just stdio.h file, there are other header files as well.

16. Back to our main discussion, so, we should agree at this moment, C/C++ program just contain functions. You will learn a lot more C/C++ standard functions that normally provided together with the compilers. This standard function collection in a compiled form normally called libraries.

17. Keep in mind that there are a lot more non-standard functions (libraries) and user-defined functions out there. Both non-standard and user-defined functions normally used to program specific tasks such as for graphic manipulation and search routines. You may also encounter other terms used for function in other programming languages such as routine and procedure. The following Figure should explain the previous example clearer.

18. We have main() function that doesn’t receive any argument and doesn’t pass any value, as the execution point. Then, in main() function, we call printf() function. During the function calls, we may receive and/or pass argument(s)/value(s). The one-way blue arrow means finding the stdio.h file for printf() definition and the two-way red arrows means the printf() function may pass and/or receive argument(s) to be processed.