Format Specifiers and Their Usage in C

C Programming: Format Specifiers and Their Usage

In C programming, format specifiers are used with functions such as printf() and scanf() to specify the type of data being displayed or accepted as input.

Common Format Specifiers

Format specifier	Data type	Example value	Usage
%d	int	25	Integer numbers
%i	int	25	Integer input/output
%f	float	12.5	Floating-point numbers
%lf	double	12.567	Double input using scanf()
%c	char	'A'	Single character
%s	char array	"Hello"	String
%u	unsigned int	25	Non-negative integer
%ld	long int	123456L	Long integer
%lld	long long int	123456789LL	Very large integer
%x	Unsigned integer	255	Hexadecimal in lowercase
%X	Unsigned integer	255	Hexadecimal in uppercase
%p	Pointer	Address	Memory address

In printf(), use %f to display a double value. In scanf(), use %lf to accept a double value.

C Program Demonstrating Format Specifiers

#include <stdio.h>

int main()

{

    int age = 18;

    float marks = 85.5f;

    double salary = 25000.75;

    char grade = 'A';

    char name[] = "Jiya";

    printf("Name: %s\n", name);

    printf("Age: %d\n", age);

    printf("Marks: %f\n", marks);

    printf("Salary: %f\n", salary);

    printf("Grade: %c\n", grade);

    printf("Percentage: %.2f%%\n", marks);

    return 0;

}

Output

Name: Jiya

Age: 18

Marks: 85.500000

Salary: 25000.750000

Grade: A

Percentage: 85.50%

Explanation

• %s displays the student's name.
• %d displays an integer.
• %f displays a floating-point value.
• %c displays a single character.
• %.2f displays a floating-point number with exactly two digits after the decimal point.
• %% displays the % symbol.
• \n moves the output to the next line.

Format Specifiers in scanf()

The scanf() function accepts input from the keyboard. The format specifier must match the variable's data type.

#include <stdio.h>

int main()

{

    int age;

    float marks;

    double salary;

    char grade;

    char name[30];

    printf("Enter your age: ");

    scanf("%d", &age);

    printf("Enter your marks: ");

    scanf("%f", &marks);

    printf("Enter your salary: ");

    scanf("%lf", &salary);

    printf("Enter your grade: ");

    scanf(" %c", &grade);

    printf("Enter your name: ");

    scanf("%29s", name);

    printf("\n--- Student Details ---\n");

    printf("Age: %d\n", age);

    printf("Marks: %.2f\n", marks);

    printf("Salary: %.2f\n", salary);

    printf("Grade: %c\n", grade);

    printf("Name: %s\n", name);

    return 0;

}

Why do we use & in scanf()?

The & operator provides the address of a variable so that scanf() can store the input in that variable. For a character array such as name, use name without &.

The space before %c in scanf(" %c", &grade) skips leftover whitespace, such as a newline from the previous input.

Width and Precision in printf()

Format specifiers can control how values are displayed.

Format	Example statement	Output
%d	printf("%d", 25);	25
%5d	printf("%5d", 25);	25
%05d	printf("%05d", 25);	00025
%f	printf("%f", 3.14159);	3.141590
%.2f	printf("%.2f", 3.14159);	3.14
%.3f	printf("%.3f", 3.14159);	3.142
%-5d	printf("%-5d", 25);	25

Usage hint:

• Width: Minimum character spaces for displaying a value.
• Precision: Number of digits after the decimal point.
• Minus (-): Left-aligns the value.
• Zero (0): Pads the value with leading zeros.

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