Using printf for output in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of printf with mixed format specifiers

What is the output of the following C code?

C

#include <stdio.h>

int main() {
    int a = 5;
    float b = 3.2f;
    printf("%d %.1f\n", a, b);
    return 0;
}

A 5 3

B 5.0 3.2

C 5 3.20

D 5 3.2

💡 Hint

Look at the format specifiers %d and %.1f and how they control output.

The %d prints the integer 5 as '5'. The %.1f prints the float with one decimal place, so 3.2 is printed as '3.2'.

❓ Predict Output

intermediate

Output of printf with escape sequences

What will this C program print?

C

#include <stdio.h>

int main() {
    printf("Hello\nWorld\t!\n");
    return 0;
}

A

Hello
World    !

B

Hello
World	!

C Hello World !

D HelloWorld!\n

💡 Hint

Remember \n is new line and \t is tab (spaces).

The \n creates a new line, so 'Hello' and 'World' appear on separate lines. The \t adds a tab space before '!'.

🔧 Debug

advanced

Identify the error in printf usage

What error will this code produce when compiled or run?

C

#include <stdio.h>

int main() {
    int x = 10;
    printf("Value is %d %f", x);
    return 0;
}

A Compilation error: missing argument for %f

B Runtime error: segmentation fault

C Output: Value is 10 (garbage value)

D Output: Value is 10 0.000000

💡 Hint

Check how many arguments printf expects vs provided.

The format string expects two arguments (%d and %f), but only one (x) is provided. This causes undefined behavior and prints garbage for %f.

🧠 Conceptual

advanced

Understanding printf return value

What does the printf function return after printing successfully?

A Always zero

B The number of characters printed

C The last character printed

D A pointer to the output string

💡 Hint

Think about what information printf might give back after printing.

printf returns the number of characters it successfully printed to the output.

📝 Syntax

expert

Which printf statement compiles and prints correctly?

Choose the option that compiles without error and prints exactly: 3.14

A printf("%.2f", 3.14159);

B printf("%2.f", 3.14159);

C printf("%f.2", 3.14159);

D printf("%.2d", 3.14159);

💡 Hint

Check the correct syntax for floating point precision in printf.

Option A uses %.2f which prints a float with 2 decimal places. Others have syntax errors or wrong specifiers.