Understanding the program in C

Let us learn the above program in detail.
Line 1 thru 4:
This is the comments in the program. It is called multiline comment. The text written within /*…*/ are ignored by the compiler.

Line 5:
This is another way to comment a text or statement. It is called single line comment. The entire line following the tag // is ignored by the compiler.

Line 6 and 7:
#include is known as pre- processor directives. It tell the compiler to include text from another file, stuffing it right into your source code.
is a file name enclosed within angle brackets. The whole statement #include tells the compiler to take text from the file stdio.h and stick it into your source code before the source code is compiled.

Line 8:
This is the start of the main function. The program execution starts from this function. main() is the name given to a set of statements. This name has to be main(). The statement that belongs to main() are enclosed within a pair of braces {}.

Line 10:
Any variable that we need to use must be declared before using it.

Line 12 thru 15:
Here the values are getting assigned to the variables.

Line 16:
Once the value of a+b is assigned to c, it needs to be displayed on the screen. We can use readymade library function to display the value on the screen. One such function is printf().

The general form of the printf() function is:
printf("", );

can contain,
%d for printing integer values
%f for printing real values
%c for printing character values
\n is a newline character. It takes the cursor to the new line. It is one of the several escape sequences available in C.

Line 9 and 17:
The function body should be enclosed in opening and closing braces.

Note:
Though comments are not necessary, it is a good programming practice to include comments in the program. Adding comments in the program increases the readability of the program. We can include as many comments as possible. A comment can be split over more than one line as shown in the above program (Line 1 thru 4). Any C statement always ends with a ;

Receiving Input
In the above program, we have assigned the value 5 and 4 to a and b respectively. But, every time we cant do so. A situation might arise wherein we need to take input from the user. Here we will learn how to receive input from the user.

scanf() – It is a standard library function in C. This function will accept the input from the user and stores it in a particular user defined variable.

The syntax of this function is:
scanf( “”, &);

can contain,
%d for printing integer values
%f for printing real values
%c for printing character values

‘&’ before the variable name is a must. ‘&’ is the ‘address of’ operator. It gives the address used by the variable in memory.

Let us consider an example:
scanf(“%d”,&a);

When we execute this statement, it will ask for input. Suppose the input given is 5. 5 will be stored as integer at the address of variable a. we can print the value stored at that address using simple printf() statement as shown below.
printf(“%d”, a);

Example:

This C tutorial is brought you by LearnCOnline.com

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45 Responses

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  10. Anonymous says:

    why or when do you use /n in printf

  11. LearnCOnline says:

    \n is a newline character. It takes the cursor to the new line. It is one of the several escape sequences available in C.

    \n is used if we want to print a character or a string in a new line.

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  13. Anonymous says:

    what does conio do?

  14. LearnCOnline says:

    conio.h is a C header file used in old MS-DOS compilers to create text user interfaces.

    Refer the below link for information in detail:
    http://en.wikipedia.org/wiki/Conio.h

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  17. Can u explain me why do u use scanf and printf instead of cin>> and cout<

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  26. Mithun Reddy says:

    hi,
    can u please explain what does ‘%d’ do in printf AND scanf statements

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  31. Anonymous says:

    @mithun reddy
    “%d” prints the value of the given value supplied to the int (integer) variable.
    If we were to be dealing with floating point variables instead of whole numbers above, “%f” would be issued within the scanf() function to print the floats value.
    Now, if anyone can mind explaining how the single character d somehow correlates with a whole number I’d appreciate it greatly seeing as %f = float, %c = character makes perfect legitimate sense.

  32. Anonymous says:

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  33. Anonymous says:

    “Now, if anyone can mind explaining how the single character d somehow correlates with a whole number I’d appreciate it greatly seeing as %f = float, %c = character makes perfect legitimate sense.”

    I have always taken it to reference “digit”

  34. Anonymous says:

    can u tell me how to give different inputs when we use scanf ?

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