To read and print data, you can use the predefined functionsscanf() andprintf() in C programs.

Example:

#include <stdio.h>void main(){    int a, b, c;    printf("Please enter any two numbers: \n");    scanf("%d %d", &a, &b);    c = a + b;    printf("The addition of two number is: %d", c);}

Output:

Please enter any two numbers:123The addition of two number is:15

In the above program, thescanf() function takes input from the user, and theprintf() function displays the output result on the screen.

Managing Input/Output

I/O operations are helpful for a program to interact with users. Cstdlib is the standard C library for input-output operations. Two essential streams play their role when dealing with input-output operations in C. These are:

1. Standard Input (stdin)
2. Standard Output (stdout)

Standard input orstdin is used for taking input from devices such as the keyboard as a data stream. Standard output orstdout is used to give output to a device such as a monitor. For I/O functionality, programmers must include thestdio header file within the program.

Reading Character In C

The easiest and simplest of all I/O operations are taking a character as input by reading that character from standard input (keyboard).getchar() function can be used to read a single character. This function is an alternative toscanf() function.

Syntax:

var_name = getchar();

Example:

#include<stdio.h>void main(){    char title;    title = getchar();}

There is another function to do that task for files:getc() which is used to accept a character from standard input.

Syntax:

int getc(FILE *stream);

Writing Character In C

Similar togetchar(), there is another function that is used to write characters, but one at a time.

Syntax:

putchar(var_name);

Example:

#include<stdio.h>void main(){    char result = 'P';    putchar(result);    putchar('\n');}

Similarly, there is another functionputc() which is used for sending a single character to the standard output.

Syntax:

int putc(int c, FILE *stream);

Formatted Input

It refers to input data that has been arranged in a specific format. This is possible in C usingscanf() function. We have already encountered this and are familiar with this function.

Syntax:

scanf("control string", arg1, arg2, ..., argn);

The field specification for reading integer input numbers is:

%w sd

Here the% sign denotes the conversion specification;w signifies the integer number that defines the field width of the number to be read.d defines the number to be read in integer format.

Example:

#include<stdio.h>void main(){    int var1= 60;    int var2= 1234;    scanf("%2d %5d", &var1, &var2);}

Input data items should have to be separated by spaces, tabs, or a new line, and the punctuation marks are not counted as separators.

Reading and Writing Strings in C

There are two popular library functions for dealing with strings in C:gets() andputs().

gets: Thechar *gets(char *str) reads a line fromstdin, keeps the string pointed to by thestr, and is terminated when the new line is read, orEOF is reached. The declaration ofgets() function is:

Syntax:

char *gets(char *str);

Where str is a pointer to an array of characters where C strings are stored.

puts: The function -int puts(const char *str) is used to write a string tostdout, but it does not includenull characters. A new line character needs to be appended to the output. The declaration is:

Syntax:

int puts(const char *str)

where thestr is the string to be written in C.