Complete Guide to % Format Specifiers in C for Beginners in 2023

Article by: Manish Methani

Last Updated: November 7, 2021 at 2:04pm IST
5 min 33 sec read

Introduction:

In C programming, the printf() function is used to output values to the console. The function uses format specifiers to determine the type of data that is being output. The % format specifiers are used to format the output and can be used with various flags and modifiers to achieve different effects.

Types of Format Specifiers:

There are several types of format specifiers in C programming, including:

• %d: prints a signed integer
• %u: prints an unsigned integer
• %f: prints a floating-point number
• %c: prints a character
• %s: prints a string
• %p: prints a pointer
• %x: prints a hexadecimal value
• %o: prints an octal value

Using the % Format Specifiers with printf():

The % format specifiers are used in conjunction with the printf() function to format the output. Here are some examples of how to use the % format specifiers with the printf() function:

Example 1: Printing a signed integer

int num = -123;
printf("The value of num is %d", num);

Output:

The value of num is -123

Example 2: Printing an unsigned integer

unsigned int num = 123;
printf("The value of num is %u", num);

Output:

The value of num is 123

Example 3: Printing a floating-point number with precision

float num = 3.14159;
printf("The value of num with 2 decimal places is %.2f", num);

Output:

The value of num with 2 decimal places is 3.14

Example 4: Printing a character

char ch = 'A';
printf("The character is %c", ch);

Output:

The character is A

Example 5: Printing a string

char str[] = "Hello, world!";
printf("The string is %s", str);

Output:

The string is Hello, world!

Example 6: Printing floating-point number with precision %.2f

 float a = 3.122222223;
printf(“a = %.2f ”, a);

Output:

a = 3.12

Example 7: Printing floating-point number with precision %.3f

 float a = 3.122222223;
printf(“a = %.3f ”, a);

Output:

a = 3.122

%.3f will restrict the values upto three decimal values.

Example 8: Printing floating-point number with precision %6.2f

 float a = 1.289999;
printf(“ a = %6.2f ”, a);

Output:

_ _1.29

where _ _ are spaces

%6.2f :- means output will be in 6 columns

Example 9: Printing floating-point number with precision %6.2f

a = 1.28999;

While printing float values using %6.2f format specifier, the final output should be of length 6. As 6.2f indicates, the total length of output should be 6 and 2 values after "." The rest part is covered with spaces. As you can see in the output image below, 2 decimal values after dot and before that we need three more values so that total length becomes 6.

Example 10: Printing floating-point number with precision %5.3f

    float a = 1.289999;
    printf(“ a = %5.3f ”, a);
    

Output: 

In this case, the final output length should be of length 5 and 3 decimal values after "." dot and 2 values before "." dot

Example 11: Printing floating-point number with precision %5.2f

float a = 1.289999;
printf(“ a = %5.2f ”, a);

Output:

In this case, the final output length should be of length 5 and 2 decimal values after "." dot and 3 values before "." dot

Example 12: Printing floating-point number with precision %5.3f

    float a = 1111.289999;
    printf(“ a = %5.3f ”, a);

Output:

a = 1111.290

In this case, before dot it contains enough digits than 5 so it will store 1111 in one block and rest in another.

Space will only be added when there are not enough digits.

Quick Recap:

Question

printf(“ %5.2f “, a);

Answer

    If a is 1111.2344444, it prints 1111.23
    If a is 11.2344444, it prints 11.23
    If a is 1.2344444 , it prints _1.234 ,
    where _ is one leading whitespace character.

Integer Output Format

Example 1:

int a = 1234;
printf(“a = %3d”, a);

Output:

a = 1234

Example 2:

int a = 123;
printf(“a = %3d”, a);

Output:

a = 123

Example 3:

int a = 12;
printf(“a = %3d”, a); 

Output:

a = _12
where, _ is space

Example 4:

int a = 1;
printf(“a = %3d”, a);

Output:

 a = _ _1
where, _ are spaces.

In conclusion, the % format specifiers are a powerful tool in C programming that allows you to format output in various ways. By using the examples provided in this tutorial, you can master the art of formatting output and improve your C programming skills.