Input & Output Functions in C

 

💻 Input & Output Functions in C (printf() and scanf())

In C (developed by Dennis Ritchie), input and output functions are used to:

• Take data from user 📥
• Display data on screen 📤

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🔹 1. printf() Function (Output) 📤

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

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✅ Syntax

printf("format specifier", variables);

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✅ Example 1

#include <stdio.h>

int main() {
    printf("Hello, World!");
    return 0;
}

👉 Output:

Hello, World!

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✅ Example 2 (with variables)

int a = 10;
printf("Value of a = %d", a);

👉 Output:

Value of a = 10

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🔹 Multiple Values Example

int a = 10;
float b = 5.5;
printf("a = %d, b = %f", a, b);

👉 Output:

a = 10, b = 5.500000

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🔹 2. scanf() Function (Input) 📥

👉 scanf() is used to take input from user

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✅ Syntax

scanf("format specifier", &variable);

👉 & = address of variable

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✅ Example 1

#include <stdio.h>

int main() {
    int a;
    scanf("%d", &a);
    printf("You entered: %d", a);
    return 0;
}

👉 Input:

5

👉 Output:

You entered: 5

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🔹 Example with Multiple Inputs

int a;
float b;

scanf("%d %f", &a, &b);
printf("a = %d, b = %f", a, b);

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🔹 Important Format Specifiers 📊

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

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🔹 Important Rules ⚠️

✔ For printf()

• No & needed
• Used to display output

✔ For scanf()

• Must use & (except for strings)
• Used to take input

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❗ Special Case (String)

char name[20];
scanf("%s", name);   // no &

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🔹 Complete Example Program 🧠

#include <stdio.h>

int main() {
    int age;
    float salary;
    char grade;

    printf("Enter age, salary, grade: ");
    scanf("%d %f %c", &age, &salary, &grade);

    printf("Age: %d\n", age);
    printf("Salary: %f\n", salary);
    printf("Grade: %c\n", grade);

    return 0;
}

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🔹 Real-Life Understanding 🤔

👉 scanf() = asking question ❓
👉 printf() = giving answer 📢

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🔹 Final Summary 📝

• printf() → output 📤
• scanf() → input 📥
• Format specifiers define data type
• & used in scanf() (except string)