Structure of a C program - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple C program with main function

What is the output of this C program when compiled and run?

C

#include <stdio.h>

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

A hello, c world!

B Hello, C world!\n

C Hello, C world!

D Compilation error

💡 Hint

Look carefully at the exact string printed and the newline character.

The program prints exactly "Hello, C world!" followed by a newline, so the output is that text on one line.

❓ Predict Output

intermediate

Value of variable after execution

What is the value of variable x after running this program?

C

#include <stdio.h>

int main() {
    int x = 5;
    x = x + 10;
    return 0;
}

A 5

B 10

C Compilation error

D 15

💡 Hint

x starts at 5 and then 10 is added.

x is initialized to 5, then 10 is added, so x becomes 15.

❓ Predict Output

advanced

Output of a program with multiple functions

What is the output of this C program?

C

#include <stdio.h>

void greet() {
    printf("Hi! ");
}

int main() {
    greet();
    printf("Welcome to C programming.\n");
    return 0;
}

A Hi! Welcome to C programming.\n

B Hi! Welcome to C programming.

C .gnimmargorp C ot emocleW !iH

D i! Welcome to C programming.

E Compilation error

💡 Hint

Look at how printf handles newlines.

The greet function prints "Hi! " without newline, then main prints the rest with newline, so output is on one line with newline at end.

❓ Predict Output

advanced

What error does this program produce?

What error will this C program produce when compiled?

C

#include <stdio.h>

int main() {
    int a = 10
    printf("Value: %d\n", a);
    return 0;
}

A Syntax error: missing semicolon

B No error, prints 'Value: 10'

C Runtime error: undefined variable

D Linker error: missing main

💡 Hint

Check each line for missing punctuation.

The line 'int a = 10' is missing a semicolon at the end, causing a syntax error.

🧠 Conceptual

expert

Number of functions in this C program

How many functions are defined in this C program?

C

#include <stdio.h>

void first() {
    printf("First\n");
}

void second() {
    printf("Second\n");
}

int main() {
    first();
    second();
    return 0;
}

A 3

B 2

C 4

D 1

💡 Hint

Count all functions including main.

There are three functions: first, second, and main.