Format specifiers - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of integer and float formatting

What is the output of this C code snippet?

C

#include <stdio.h>

int main() {
    int a = 42;
    float b = 3.14159;
    printf("%5d %.2f\n", a, b);
    return 0;
}

A 42 3.14

B 42 3.14

C 42 3.1416

D 42 3.14159

💡 Hint

Look at the width and precision in the format specifiers.

The %5d means print the integer right-aligned in a field 5 characters wide, so 42 is padded with 3 spaces. The %.2f means print the float with 2 digits after the decimal point, rounding 3.14159 to 3.14.

❓ Predict Output

intermediate

Output of string and character formatting

What will this C program print?

C

#include <stdio.h>

int main() {
    char c = 'A';
    char *str = "Hi";
    printf("%3c %5s\n", c, str);
    return 0;
}

A A Hi

B A Hi

C A Hi

D iH A

💡 Hint

Check the width specifiers for character and string.

%3c prints the character right-aligned in 3 spaces, so two spaces then 'A'. %5s prints the string right-aligned in 5 spaces, so three spaces then 'Hi'.

❓ Predict Output

advanced

Output with left alignment and zero padding

What is the output of this code?

C

#include <stdio.h>

int main() {
    int x = 7;
    printf("%-5d %05d\n", x, x);
    return 0;
}

A 70000 7

B 7 00007

C 7 7

D 7 00007

💡 Hint

Look at the minus sign and zero in the format specifiers.

%-5d means print integer left-aligned in 5 spaces, so '7' then 4 spaces. %05d means print integer padded with zeros to width 5, so '00007'.

❓ Predict Output

advanced

Output of pointer and hexadecimal formatting

What will this program print?

C

#include <stdio.h>

int main() {
    int num = 255;
    printf("%p %x %X\n", (void*)&num, num, num);
    return 0;
}

A 7ffee3bff6ac ff FF

B 0x7ffee3bff6ac ff FF

C 0x7ffee3bff6ac 0xff 0xFF

D 0x7ffee3bff6ac 255 255

💡 Hint

%p prints pointer with 0x prefix, %x and %X print hex lowercase and uppercase without 0x.

%p prints the pointer address with 0x prefix. %x prints the integer in lowercase hex without 0x. %X prints uppercase hex without 0x. The actual pointer address varies but includes 0x prefix.

❓ Predict Output

expert

Output of mixed format specifiers with precision and width

What is the output of this C program?

C

#include <stdio.h>

int main() {
    double val = 123.456789;
    printf("%10.3f %.5s %04d\n", val, "HelloWorld", 9);
    return 0;
}

A 123.457 Hello 0009

B 123.456789 Hello 0009

C 123.457 HelloWorld 9

D 123.456 Hello 9

💡 Hint

Check width and precision for float, string, and integer.

%10.3f prints float in 10 spaces with 3 decimals, rounding 123.456789 to 123.457. %.5s prints first 5 chars of string "HelloWorld" as "Hello". %04d prints integer padded with zeros to width 4, so 0009.