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Input & Output in C

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Introduction

In any programming language, interacting with the user is very important.
This is done using Input and Output operations.

• Output → Displaying data to the user
• Input → Taking data from the user

In C, we mainly use:

• printf() → for output
• scanf() → for input

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Header File Required

To use input and output functions, include:

#include <stdio.h>

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printf() Function

printf() is used to display output on the screen.

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Syntax

printf("message");

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Example

#include <stdio.h>

int main() {
    printf("Welcome to Dharani Tech Edu Hub!");
    return 0;
}

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Output

Welcome to Dharani Tech Edu Hub!

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Using Variables with printf()

#include <stdio.h>

int main() {
    int age = 20;
    printf("Age = %d", age);
    return 0;
}

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Output

Age = 20

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Format Specifiers

Used to display different data types:

Data Type	Format Specifier
int	%d
float	%f
char	%c
double	%lf

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scanf() Function (Input)

scanf() is used to take input from the user.

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Syntax

scanf("format_specifier", &variable);

👉 & is called address-of operator

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Example

#include <stdio.h>

int main() {
    int age;
    printf("Enter your age: ");
    scanf("%d", &age);

    printf("You entered: %d", age);

    return 0;
}

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Sample Output

Enter your age: 18
You entered: 18

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Multiple Inputs

#include <stdio.h>

int main() {
    int a, b;

    printf("Enter two numbers: ");
    scanf("%d %d", &a, &b);

    printf("Sum = %d", a + b);

    return 0;
}

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Output

Enter two numbers: 5 10
Sum = 15

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Important Notes

• ✔ Always use & before variable in scanf()
• ✔ Match format specifier with data type
• ✔ Use \n for new line

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🔹 Common Mistakes

• ❌ Forgetting & in scanf()
• ❌ Wrong format specifier
• ❌ Missing #include <stdio.h>
• ❌ Not initializing variables properly

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Pro Tips

• ✔ Use clear prompts (Enter value:)
• ✔ Validate user input (advanced level)
• ✔ Practice input/output programs daily
• ✔ Combine multiple inputs and outputs

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Difference Between printf() and scanf()

Difference Between printf() and scanf()

This table explains the key differences between printf() and scanf() functions in C programming.

Feature	printf()	scanf()
Purpose	Output	Input
Usage	Displays data	Takes user input
Symbol	No & needed	& required

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Conclusion

Input and Output functions are the basic building blocks of any C program. They allow interaction between the user and the program.

Mastering printf() and scanf() is essential before moving to advanced topics.

👉 This article is part of Dharani Tech Edu Hub — where learning programming is made simple and practical.