C Input-Output (I/O)

In this tutorial, you will learn how to use scanf() function to take input from the user, and printf() function to show output to the client.

C Output

In C programming, printf() is one of the main output function. The capacity sends an arranged yield to the screen. For instance,

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Example 1: C Output

#include <stdio.h>    
int main()
{ 
    // Displays the string inside quotations
    printf("C Programming");
    return 0;
}

Output

C Programming

How does this program work?

All valid C programs must contain the main() function. The code execution begins from the start of the main() function.
The printf() is a library function to send formatted output to the screen. The function prints the string inside quotations.
To use printf() in our program, we need to include stdio.h header file using the #include <stdio.h> statement.
The return 0; statement inside the main() function is the “Exit status” of the program. It’s optional.

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Example 2: Integer Output

#include <stdio.h>
int main()
{
    int testInteger = 5;
    printf("Number = %d", testInteger);
    return 0;
}

Output

Number = 5

We use the %d design specifier to print int types. Here, the %d inside the citations will be supplanted by the estimation of testInteger.

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Example 3: float and double Output

#include <stdio.h>
int main()
{
    float number1 = 13.5;
    double number2 = 12.4;

    printf("number1 = %f\n", number1);
    printf("number2 = %lf", number2);
    return 0;
}

Output

number1 = 13.500000
number2 = 12.400000

To print float, we use the %f format specifier. Similarly, we use %lf to print double values.

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Example 4: Print Characters

#include <stdio.h>
int main()
{
    char chr = 'a';    
    printf("character = %c.", chr);  
    return 0;
} 

Output

character = a

To print char, we use the %c format specifier.

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C Input

In C programming, scanf() is one of the commonly used functions to take input from the client. The scanf() function reads formatted input from the standard input such as keyboards.

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Example 5: Integer Input/Output

#include <stdio.h>
int main()
{
    int testInteger;
    printf("Enter an integer: ");
    scanf("%d", &testInteger);  
    printf("Number = %d",testInteger);
    return 0;
}

Output

Enter an integer: 4
Number = 4

Here, we have used the %d design specifier inside the scanf() capacity to take int contribution from the client. when the client enters a number, it is put away in the testInteger variable.

Notice, that we have used &testInteger inside scanf(). It is on the grounds that &testInteger gets the location of testInteger, and the value entered by the user is stored in that address.

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Example 6: Float and Double Input/Output

#include <stdio.h>
int main()
{
    float num1;
    double num2;

    printf("Enter a number: ");
    scanf("%f", &num1);
    printf("Enter another number: ");
    scanf("%lf", &num2);

    printf("num1 = %f\n", num1);
    printf("num2 = %lf", num2);

    return 0;
}

Output

Enter a number: 12.523
Enter another number: 10.2
num1 = 12.523000
num2 = 10.200000

We use %f and %lf format specifier for float and double respectively.

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Example 7: C Character I/O

#include <stdio.h>
int main()
{
    char chr;
    printf("Enter a character: ");
    scanf("%c",&chr);     
    printf("You entered %c.", chr);  
    return 0;
}   

Output

Enter a character: g
You entered g.

When a character is entered by the client in the above program, the character itself isn’t put away. Rather, a whole number worth (ASCII value) is stored.

What’s more, when we show that worth utilizing %c text design, the entered character is shown. In the event that we use %d to show the character, it’s ASCII value is printed.

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Example 8: ASCII Value

#include <stdio.h>
int main()
{
    char chr;
    printf("Enter a character: ");
    scanf("%c", &chr);     

    // When %c is used, a character is displayed
    printf("You entered %c.\n",chr);  

    // When %d is used, ASCII value is displayed
    printf("ASCII value is % d.", chr);  
    return 0;
}

Output

Enter a character: g
You entered g.
ASCII value is 103.

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I/O Multiple Values

Here’s how you can take multiple inputs from the user and display them.

#include <stdio.h>
int main()
{
    int a;
    float b;

    printf("Enter integer and then a float: ");
  
    // Taking multiple inputs
    scanf("%d%f", &a, &b);

    printf("You entered %d and %f", a, b);  
    return 0;
}

Output

Enter integer and then a float: -3
3.4
You entered -3 and 3.400000

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Format Specifiers for I/O

As you can see from the above examples, we use

%d for int
%f for float
%lf for double
%c for char
Here’s a list of commonly used C data types and their format specifiers.

Data Type	Format Specifier
int	%d
char	%c
float	%f
double	%lf
short int	%hd
unsigned int	%u
long int	%li
long long int	%lli
unsigned long int	%lu
unsigned long long int	%llu
signed char	%c
unsigned char	%c
long double	%Lf

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Please feel free to give your comment if you face any difficulty here.

For more Articles click on the below link.

C Introduction