Format specifiers - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print an integer variable using printf.

C

#include <stdio.h>

int main() {
    int num = 10;
    printf("[1]\n", num);
    return 0;
}

Drag options to blanks, or click blank then click option'

A%d

B%c

C%f

D%s

Attempts:

3 left

💡 Hint

Common Mistakes

Using %f for integers causes incorrect output.

Using %c prints a single character, not an integer.

The %d format specifier is used to print integers in C.

2fill in blank

medium

Complete the code to print a floating-point number with printf.

C

#include <stdio.h>

int main() {
    float pi = 3.14f;
    printf("[1]\n", pi);
    return 0;
}

Drag options to blanks, or click blank then click option'

A%d

B%s

C%c

D%f

Attempts:

3 left

💡 Hint

Common Mistakes

Using %d prints only the integer part, not the decimal.

Using %c or %s is incorrect for numbers.

The %f format specifier is used to print floating-point numbers in C.

3fill in blank

hard

Fix the error in the code to correctly print a character.

C

#include <stdio.h>

int main() {
    char letter = 'A';
    printf("[1]\n", letter);
    return 0;
}

Drag options to blanks, or click blank then click option'

A%d

B%f

C%c

D%s

Attempts:

3 left

💡 Hint

Common Mistakes

Using %d prints the ASCII code, not the character.

Using %s expects a string, not a single char.

The %c format specifier is used to print a single character in C.

4fill in blank

hard

Fill both blanks to print a string and an integer correctly.

C

#include <stdio.h>

int main() {
    char name[] = "Bob";
    int age = 25;
    printf("Name: [1], Age: [2]\n", name, age);
    return 0;
}

Drag options to blanks, or click blank then click option'

A%s

B%d

C%f

D%c

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the format specifiers causes wrong output.

Using %f for integers or strings causes errors.

%s prints strings and %d prints integers in C.

5fill in blank

hard

Fill all three blanks to print a float with two decimals, a character, and a string.

C

#include <stdio.h>

int main() {
    float price = 9.99f;
    char grade = 'A';
    char product[] = "Book";
    printf("Price: [1], Grade: [2], Product: [3]\n", price, grade, product);
    return 0;
}

Drag options to blanks, or click blank then click option'

A%.2f

B%c

C%s

D%d

Attempts:

3 left

💡 Hint

Common Mistakes

Using %f without precision prints many decimals.

Mixing up %c and %s causes wrong output.

%.2f prints a float with 2 decimal places, %c prints a character, and %s prints a string.

Practice

1. Which format specifier is used to print an integer value in C using printf?

easy

A. %d

B. %f

C. %c

D. %s

Solution

1. Step 1: Understand integer data type printing

   The %d specifier is used to print integer values in C.

2. Step 2: Identify other specifiers

   %f is for floats, %c for characters, and %s for strings.

3. Final Answer:

   %d -> Option A

4. Quick Check:

   Integer print = %d [OK]

Hint: Use %d for integers in printf [OK]

Common Mistakes:

• Using %f for integers
• Confusing %c with %d
• Using %s for numbers

2. Which of the following is the correct way to print a character variable ch in C?

easy

A. printf("%c", ch);

B. printf("%s", ch);

C. printf("%d", ch);

D. printf("%f", ch);

Solution

1. Step 1: Identify character format specifier

   The correct specifier for a character is %c.

2. Step 2: Check other options

   %s is for strings, %d for integers, and %f for floats, so they are incorrect for a character.

3. Final Answer:

   printf("%c", ch); -> Option A

4. Quick Check:

   Character print = %c [OK]

Hint: Use %c to print single characters [OK]

Common Mistakes:

• Using %s for characters
• Using %d which prints ASCII code
• Using %f for characters

3. What will be the output of the following code?

int x = 10;
float y = 5.5;
printf("%d %f", x, y);

medium

A. 10 5.5

B. 10 5.500000

C. 5.5 10

D. Error

Solution

1. Step 1: Understand format specifiers in printf

   %d prints integer as is, %f prints float with 6 decimal places by default.

2. Step 2: Match variables to specifiers

   x is 10 (int), printed by %d. y is 5.5 (float), printed by %f as 5.500000.

3. Final Answer:

   10 5.500000 -> Option B

4. Quick Check:

   Integer and float print with %d and %f [OK]

Hint: Floats print with 6 decimals by default using %f [OK]

Common Mistakes:

• Expecting %f to print fewer decimals
• Swapping variable order
• Using %d for float causing wrong output

4. Identify the error in the following code snippet:

char name[10];
scanf("%c", name);

medium

A. No error, code is correct

B. Use &name instead of name

C. Use %d instead of %c

D. Use %s instead of %c to read string

Solution

1. Step 1: Understand scanf format specifiers

   %c reads a single character, but name is an array for a string.

2. Step 2: Correct specifier for string input

   To read a string into name, use %s which reads until whitespace.

3. Final Answer:

   Use %s instead of %c to read string -> Option D

4. Quick Check:

   String input needs %s in scanf [OK]

Hint: Use %s to read strings with scanf [OK]

Common Mistakes:

• Using %c to read strings
• Forgetting & with non-array variables
• Using %d for characters

5. You want to print a floating-point number float pi = 3.14159; with only 2 decimal places. Which printf statement is correct?

hard

A. printf("%2f", pi);

B. printf("%f.2", pi);

C. printf("%.2f", pi);

D. printf("%f", pi);

Solution

1. Step 1: Understand precision in format specifiers

   To limit decimal places, use %.2f where 2 is the number of decimals.

2. Step 2: Check other options

   %2f sets minimum width, not decimals; %f.2 is invalid; %f prints 6 decimals by default.

3. Final Answer:

   printf("%.2f", pi); -> Option C

4. Quick Check:

   Use %.2f to print 2 decimals [OK]

Hint: Use %.2f to print float with 2 decimals [OK]

Common Mistakes:

• Using %2f expecting 2 decimals
• Placing .2 after %f incorrectly
• Using %f prints 6 decimals by default