Writing first C program - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this C program?

Look at the code below. What will it print when run?

C

#include <stdio.h>

int main() {
    printf("Hello, C World!\n");
    return 0;
}

A Compilation error

B Hello, C World!

C Hello, C World!\n

D hello, c world!

💡 Hint

Remember that printf prints the string exactly, and \n means new line.

The program prints the string inside printf exactly, including the new line. So it outputs 'Hello, C World!' followed by a new line.

❓ Predict Output

intermediate

What is the output of this C program with variables?

What will this program print when run?

C

#include <stdio.h>

int main() {
    int a = 5;
    int b = 3;
    printf("Sum is %d\n", a + b);
    return 0;
}

A Sum is 8

B Sum is 53

C Compilation error

D Sum is %d

💡 Hint

The %d in printf is replaced by the integer value of a + b.

The program adds 5 and 3 to get 8, then prints 'Sum is 8' followed by a new line.

❓ Predict Output

advanced

What error does this C program produce?

What error will this program cause when compiled?

C

#include <stdio.h>

int main() {
    printf("Missing semicolon")
    return 0;
}

A No error, prints 'Missing semicolon'

B Runtime error

C Syntax error: expected ';' before 'return'

D Linker error

💡 Hint

Check if all statements end with a semicolon.

The printf statement is missing a semicolon at the end, causing a syntax error during compilation.

❓ Predict Output

advanced

What is the output of this C program with a loop?

What will this program print when run?

C

#include <stdio.h>

int main() {
    for (int i = 1; i <= 3; i++) {
        printf("%d ", i);
    }
    return 0;
}

A 1 2 3

B 123

C 1 2 3\n

D Compilation error

💡 Hint

The loop prints numbers 1 to 3 separated by spaces.

The loop prints '1 ', then '2 ', then '3 ', all on the same line with spaces.

🧠 Conceptual

expert

How many items are printed by this C program?

How many times does the printf statement run and print a number?

C

#include <stdio.h>

int main() {
    int count = 0;
    for (int i = 0; i < 5; i++) {
        if (i % 2 == 0) {
            printf("%d ", i);
            count++;
        }
    }
    printf("\nCount: %d", count);
    return 0;
}

A 2

B 5

C 4

D 3

💡 Hint

Count how many numbers from 0 to 4 are even.

The loop prints numbers 0, 2, and 4 because they are even. So printf runs 3 times.