Input/Output Functions in C

Input and output functions are essential for interacting with users in C programming. They allow you to display information on the screen and receive input from the keyboard.

1. printf() Function

The printf() function is used to print formatted output to the standard output (usually the console).

Syntax

int printf(const char *format, ...);

Parameters

• format: A string that specifies the format of the output.
• ...: Additional arguments that are formatted according to the format specifiers in the format string.

Common Format Specifiers

Example

#include <stdio.h>
 
int main() {
    int a = 10;
    float b = 20.5;
    char ch = 'A';
    char str[] = "Hello, World!";
 
    printf("Integer: %d\n", a);
    printf("Float: %.2f\n", b);
    printf("Character: %c\n", ch);
    printf("String: %s\n", str);
 
    return 0;
}

Output

Integer: 10
Float: 20.50
Character: A
String: Hello, World!

2. scanf() Function

The scanf() function is used to read formatted input from the standard input (usually the keyboard).

Syntax

int scanf(const char *format, ...);

Parameters

• format: A string that specifies the expected input format.
• ...: Pointers to variables where the input will be stored.

Common Format Specifiers

Example

#include <stdio.h>
 
int main() {
    int a;
    float b;
    char ch;
    char str[100];
 
    printf("Enter an integer: ");
    scanf("%d", &a);
    printf("Enter a float: ");
    scanf("%f", &b);
    printf("Enter a character: ");
    scanf(" %c", &ch); // Note the space before %c to consume newline
    printf("Enter a string: ");
    scanf("%s", str);
 
    printf("\nYou entered:\n");
    printf("Integer: %d\n", a);
    printf("Float: %.2f\n", b);
    printf("Character: %c\n", ch);
    printf("String: %s\n", str);
 
    return 0;
}

Output

Enter an integer: 42
Enter a float: 3.14
Enter a character: C
Enter a string: Hello

You entered:
Integer: 42
Float: 3.14
Character: C
String: Hello

3. getchar() Function

The getchar() function reads a single character from standard input.

Syntax

int getchar(void);

Description

• Returns the next character from the input buffer.
• It reads characters one by one until the Enter key is pressed.

Example

#include <stdio.h>
 
int main() {
    char ch;
 
    printf("Enter a character: ");
    ch = getchar(); // Read a single character
    printf("You entered: %c\n", ch);
 
    return 0;
}

Output

Enter a character: A
You entered: A

4. putchar() Function

The putchar() function writes a single character to standard output.

Syntax

int putchar(int ch);

Description

• Writes the specified character to the output.

Example

#include <stdio.h>
 
int main() {
    char ch = 'A';
 
    printf("Character to output: ");
    putchar(ch); // Output the character
    putchar('\n'); // Print a new line
 
    return 0;
}

Output

Character to output: A

Summary of Input/Output Functions in C

• printf(): Used for formatted output.
• scanf(): Used for formatted input.
• getchar(): Reads a single character from input.
• putchar(): Outputs a single character to the screen.

Understanding these functions is crucial for effective interaction with users in C programs.

Key Points:

• printf() is for displaying output, while scanf() is for receiving input.
• getchar() and putchar() are simpler functions for single-character input/output.