Structure of C programs

          PREPROCESSOR DIRECTIVE SECTION

        ↓

          GLOBAL SECTION

        ↓

          MAIN SECTION

        ↓

          USER DEFINED SECTION

EXAMPLE:-

C program structure

⇒ #include :-  

• It is a preprocessor directive which is used to include header file in a program .
• All preprocessor directive must be started with "#" symbol.
• There is  no space between # and include.

     syntax:-

            #include<header file>

 ⇒HEADER FILE:-

• It is a special file that consist of all predefined function.
• The file extension of header file is ".h".
• It is mainly used to access function in a program.    

  There are some header file in C:-

• stdio.h    
• conio.h
• math.h
• string.h
• ctype.h
• alloc.h
• malloc.h
• dos.h
• graphics.h
• process.h
• stdlib.h
• etc.

⇒ MAIN( ) FUNCTION :-

• It is an entry point in which we write source code according to requirement ,so it is called user defined function.
• The elements of program must be started with main function.

 In C

      syntax:-

                     main( )

                     {                                        //starts execution

                       block of statements;

                      }                                       //ends execution

In C++

        syntax 1:-

                      void main( )

                      {

                        block of statements;

                        }

  "NOTE: void is the keyword that specifies main( ) function does not return any value."

        syntax 2:-

                      int main( )

                         {

                           block of statements;

                          }

  "NOTE: here main( ) function can return any integer type value."                    

⇒ clrscr( ):-

• This function is used to clear the previous output on the console.
• This funcion is available in "conio.h" header file.

    syntax:-

                  clrscr( );

             

⇒ getch( ):-

• It is mainly used to input one character at a time, so it holds the output screen for viewing output.
• It is available in "conio.h" headeer file.   

   syntax:-  

            getch( );