Why functions are needed - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of code without functions

What is the output of this C code that repeats a task without using functions?

C

#include <stdio.h>

int main() {
    int i;
    for(i = 1; i <= 3; i++) {
        printf("Hello, user!\n");
    }
    for(i = 1; i <= 3; i++) {
        printf("Hello, user!\n");
    }
    return 0;
}

A Hello, user!\nHello, user!\nHello, user!\nHello, user!\nHello, user!\nHello, user!\n

B Compilation error

C Hello, user!\nHello, user!\nHello, user!\nHello, user!\n

D Hello, user!\nHello, user!\nHello, user!\n

💡 Hint

Look at how many times the print statement runs in total.

The code prints "Hello, user!" three times in the first loop and three times again in the second loop, totaling six times.

❓ Predict Output

intermediate

Output of code using functions

What is the output of this C code that uses a function to print a message multiple times?

C

#include <stdio.h>

void greet() {
    printf("Hello, user!\n");
}

int main() {
    int i;
    for(i = 1; i <= 3; i++) {
        greet();
    }
    for(i = 1; i <= 3; i++) {
        greet();
    }
    return 0;
}

A Compilation error

B Hello, user!\nHello, user!\nHello, user!\n

C Hello, user!\nHello, user!\nHello, user!\nHello, user!\n

D Hello, user!\nHello, user!\nHello, user!\nHello, user!\nHello, user!\nHello, user!\n

💡 Hint

The function greet() is called six times in total.

The greet() function prints the message once. It is called three times in each loop, so the message prints six times total.

🧠 Conceptual

advanced

Why use functions instead of repeating code?

Which of the following is the main reason to use functions in C programming?

A To make the program run faster by avoiding loops

B To organize code, avoid repetition, and make it easier to maintain

C To use more memory for storing variables

D To make the program harder to read and understand

💡 Hint

Think about how functions help when you want to change something in many places.

Functions help organize code by grouping repeated tasks. This avoids repeating code and makes it easier to update and maintain.

🔧 Debug

advanced

Identify the error in function usage

What error will this C code produce?

C

#include <stdio.h>

void greet() {
    printf("Hello!\n");
}

int main() {
    greet;
    return 0;
}

A No output, because greet is not called properly

B Runtime error: function greet not found

C Compilation error: expected expression before ';' token

D Output: Hello!

💡 Hint

Check how functions are called in C.

In C, functions must be called with parentheses. Writing 'greet;' is just a reference, not a call, causing a syntax error.

❓ Predict Output

expert

Output of nested function calls

What is the output of this C program with nested function calls?

C

#include <stdio.h>

void printA() {
    printf("A");
}

void printB() {
    printA();
    printf("B");
}

int main() {
    printB();
    printf("C\n");
    return 0;
}

A

ABC

B

ACB

C

BAC

D

CAB

💡 Hint

Follow the order of function calls and prints step by step.

printB() calls printA() first, which prints 'A'. Then printB() prints 'B'. Finally, main prints 'C' with a newline.