Basic form of C program , Comments inside C program , main() , printf() function

Basic form of C Programming

#include<stdio.h>
int main(){
int a , b , c;
 
a = 15;
b = 10;
c=a+b;
printf("Sum of a and b :%d",c);
return 0;
 
}

If you look at the above program and previous example , you will notice that there are certain rules and pattern followed in C language . The rules are :

There is common , #include<stdio.h> , that is called header file , which contain the set of predefined standard library function . In C program , necessarily contain header file , to use input and output functionality in the program . In C program , for input we use scanf() library function and for output we use printf() library function .
All the statement written in C programming language place inside the curly braces {} .
Every C statement must end with a semicolon ; , that act as statement terminator and all statement should be in lower case letters .
Blank spaces may be inserted between two words to improve the readability of the statement .

How to Write comments in C programming Language

Comments are necessary for any programming language for understanding the source code . It is a good practice to begin a program with comment , which indicate the purpose of the program i.e., date , title of the program . Comments are also necessary but not important ,to understand the source code in later for modification or updation . Also implementation of comment beside the source code statement , help us to understand the logic .

Comment in C program :

There are basically two ways to write comments in C programming language .

Comment should enclose inside /* */ .
Write comment start with // .

Let's understand with example :

/* Printing Integer , decimal and character */
#include<stdio.h>
int main()
{int a=20; 
 
float b=25.5; 
 
char c_val='g';
 
printf("In this program the integer varible is : %i\n",a);
printf("In this program the integer varible is : %f\n",b);
printf("In this program the integer varible is : %c",c_val);
return 0;
}

If you look at the first line of above program , you will notice comment . C compiler just ignore the first line .

Multi-line comment in C program:

Multi-line comment should be written also within inside the /* */ .

/* Printing Integer , decimal and character 
integer variable must be declare with int ,
decimal variable must also be declare with float
*/
#include<stdio.h>
int main()
{int a=20; 
 
float b=25.5; 
 
char c_val='g';
 
printf("In this program the integer varible is : %i\n",a);
printf("In this program the integer varible is : %f\n",b);
printf("In this program the integer varible is : %c",c_val);
return 0;
}

Single line comment in C program:

Single line comment should be written within // .

/* Printing Integer , decimal and character 
integer variable must be declare with int ,
decimal variable must also be declare with float
*/
#include<stdio.h>
int main()
{int a=20; // this is integer variable
 
float b=25.5; // this is float variable
 
char c_val='g';
 
printf("In this program the integer varible is : %i\n",a);
printf("In this program the integer varible is : %f\n",b);
printf("In this program the integer varible is : %c",c_val);
return 0;
}

Note :- If you write comment with /* */ , comment should be enclosed .

/* Printing Integer , decimal and character 
integer variable must be declare with int ,
decimal variable must also be declare with float
 
#include<stdio.h>
int main()
{int a=20; // this is integer variable
 
float b=25.5; // this is float variable
 
char c_val='g';
 
printf("In this program the integer varible is : %i\n",a);
printf("In this program the integer varible is : %f\n",b);
printf("In this program the integer varible is : %c",c_val);
return 0;
}

If you look at above program from first line to third line , you will notice that , we remove */ , I mean to say , we wrote comments , but did not close it. As a result , compiler simply return an error - C Files\variable.c [Error] unterminated comment

main() Function in C language:

main() is very important for writing code in C language . There are multiple function in C language , main() is one of them . A function is container for set of statements . All statement belongs to the main() are enclosed within a pair of curly braces{} .

Function in C language also return a value . main() function always return an integer value , thats why there is int before main() .

Syntax:

#include<stdio.h>
int main()
{
statement 1;
statement 2;
return 0;

}

printf() function in C language:

Suppose you just write a simple code to multiply 50 with 87 . Lets write the code ,

#include<stdio.h>
int main()
{
int a =50;
int b =87;
int c;
c=a*b; // multiplication of 50 and 87    
return 0;
}

If you run the above code , C compiler will simply run the code and as a output it will give something like below .

--------------------------------
Process exited after 0.06084 seconds with return value 0
Press any key to continue . . .

Compiler run the above code , but you will not be able to see the multiplication result . To see the desired result or as you want to print something by the compiler , C language has inbuilt function called printf() .

To able to use printf() function , it is necessary to use #include<stdio.h> at the beginning of the program . #include is a pre-processor directive.

Syntax of use of printf() function :

printf("format string", variable);

format string -> Which type of output want to print .

%i or %d for printing integer type(5) .
%f for printing real value (5.5) .
%c for printing character value(a) .

For better understanding , lets modify the above code ,

#include<stdio.h>
int main()
{
int a =50;
int b =87;
int c;
c=a*b; // multiplication of 50 and 87
printf("%i",c);   /*printing the multiplication value*/    
return 0;
}

Output will be something like this ,

4350
--------------------------------
Process exited after 0.1151 seconds with return value 0
Press any key to continue . . .

Let re-modify the above code again ,

#include<stdio.h>
int main()
{
int a =50;
int b =87;
int c;
c=a*b; // multiplication of 50 and 87
printf("Multiplication of 50 and 87: %i",c);   /*printing the multiplication value*/    
return 0;
}

Output of the above code something like this ,

Multiplication of 50 and 87: 4350
--------------------------------
Process exited after 0.0691 seconds with return value 0
Press any key to continue . . .

From , above code you will easily understand , that how to use printf() function in C language .

Next-> scanf() function and C operator