What Is scanf() and printf() Function

C is a functional programming language. C provides library of functions to perform input-output operations. This library is called a standard input-output library. It is denoted by stdio. The header file containing such library functions is called stdio.h. Some standard input-output functions in C are:

1. printf()
2. scanf()
3. gets()
4. puts()
5. getch()
6. getchar()
7. putchar()
8. getche()

Mainly there are two types of input-output(I/O) statements:

1. Formatted I/O statements
2. Unformatted I/O statements

scanf() and printf() are formatted input and output statements where as getchar(), gets() and putchar(),puts() are unformatted input and output statements.

Lets have a look on Two most widely used INPUT and OUTPUT Functions:

Scanf() Function:

• To read the values for the variables in a program from the keyboard , C provides a function called scanf(). 
• It is equivalent to the READ statement. 
• It is included in stdio.h header file. 

The syntax of scanf() :

scanf(" control string" , address_list );

Where

Control string => It is asequence of one or more character group. Each character group is a combination of the % symbol and one of the conversion character. Control string specifies the type of the values which are to be supplied to the variable.

Address_list => Address of the memory location where the value of the input variables should be stored.

NOTE: The character f in the scanf() shows the format(" ") of this function.

Printf() Function:

• It is used to display the data on the monitor. 
• It is included in the stdio.h header file. 

The syntax of printf() is:

printf("Control string" , variable);

Control string => this specifies the type and format of the values to be displayed.

Variable => list of variables to be displayed.

NOTE: The character f in the printf() shows the format(" ") of this function

Header files:

• Files that are placed before main() of a C program are called header files. 
• The header files are used to provide necessary information. 
• Header files contain library functions. 
• They can be written with in the angle brackets or the double quotes. 
• The header files usually contains .h as extension. 
• They are entered into the source program via #include directive.

Preprocessor directive:

• C processor is a collection of special statements are called preprocessor directive. 
• It is executed before the C program is complied. 
• The preprocessor directive begin with the # symbol and followed by either the include or define keyword. 
• They are used to include files into a program.

Example:  
#include<stdio.h>
where  #include is a preprocessor directive and <stdio.h> is a header file.