INTRODUCTION

  1) The C language is a low level language with characters, numbers and constants

2) The only way to learn a new programming language is by writing programs in it. While going into the structure of C program we will see a small example, if we want to print "hiii to all" in C language we have to write a program which is as follows

          #include<stdio.h>

             main()  

             {       

                printf("hiii to all");  

             }

3) The C program is saved by an extension .C, If we want to run this code first
we have to do compilation, to compile we have to use command cc filename.c ,  if the file name you want to give as hiii so you have to save it as hiii.c and for compilation we have to write cc hiii.c then if no errors are displayed , then we have to run the program we have to type the command a. out then it prints hiii to all.

4) Now you got an idea how we write a program in C language. Let’s see what is the structure of a C program

       

       

Let u know about each thing in detail

11)   Documentation section: In this section we can declare multiline function(*------*) in this function we can write the name of the program or any matter which is not considered by the compiler and we can also declare comment lines(//--------)where we can write what actually the meaning of the particular line

           For example:

            printf("hiii to all);     //it prints hiii to all on the screen

  2)   Link section: In this section we declare predefined functions like #include<stdio.h> which is also called as library function in this it includes the definitions of what we declare in the program like printf(), scanf() etc.,

  3)   Definition function: Some of the constants are not included in the library function like pi value and if you want to define our own values for a particular variable we can define in this section example:#define Pi 3.1717.It is not compulsion to define this section in all programs it is our requirement to  define in a program

  4)   Global declaration section: A local variable is a variable that is declared inside a function. A global variable is a variable that is declared outside all functions. A local variable can only be used in the function where it is declared. A global variable can be used in all functions .Local variable is different than global variables, the constants like int a=2; if declared in a particular function it is a local variable and if it is declared in main() part it is global declaration

  5)   Main() function section: As the name indicates this section is heart of the program without this the program  cannot be executed if you do not write this section the program is invalid

  6)   Subprogram section: This section is wriiten inside main section whatever we write in the main() is logic let us see an example program to add two numbers

      #include<stdio.h>   //link section

        main()              //main() function

       {  

           int a,b,c;        //global declarations

            a=10;

            b=5;                   

            c=a+b;

            printf("the sum is c=%d,"c);

    }