Function calling - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to call the function greet.

C

#include <stdio.h>

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

int main() {
    [1];
    return 0;
}

Drag options to blanks, or click blank then click option'

Agreet()

Bgreet

Cgreet[]

Dcall greet()

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the parentheses when calling the function.

Using incorrect syntax like brackets or keywords.

To call a function in C, you write its name followed by parentheses, like greet().

2fill in blank

medium

Complete the code to call the function add with arguments 5 and 3.

C

#include <stdio.h>

int add(int a, int b) {
    return a + b;
}

int main() {
    int result = [1];
    printf("%d\n", result);
    return 0;
}

Drag options to blanks, or click blank then click option'

Aadd{5, 3}

Badd[5, 3]

Cadd 5, 3

Dadd(5, 3)

Attempts:

3 left

💡 Hint

Common Mistakes

Using spaces instead of parentheses for arguments.

Using brackets or braces instead of parentheses.

To call a function with arguments, use the function name followed by parentheses containing the arguments separated by commas, like add(5, 3).

3fill in blank

hard

Fix the error in the function call to multiply with arguments 4 and 7.

C

#include <stdio.h>

int multiply(int x, int y) {
    return x * y;
}

int main() {
    int product = multiply[1];
    printf("%d\n", product);
    return 0;
}

Drag options to blanks, or click blank then click option'

A(4, 7)

B[4, 7]

C{4, 7}

D4, 7

Attempts:

3 left

💡 Hint

Common Mistakes

Using square brackets or curly braces instead of parentheses.

Omitting parentheses entirely.

Function arguments must be inside parentheses separated by commas, like multiply(4, 7).

4fill in blank

hard

Fill both blanks to call the function divide with arguments 10 and 2, and store the result in result.

C

#include <stdio.h>

double divide(double a, double b) {
    return a / b;
}

int main() {
    double [1] = [2];
    printf("%.2f\n", result);
    return 0;
}

Drag options to blanks, or click blank then click option'

Aresult

Bdivide(10, 2)

Cdivide(2, 10)

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name different from the one printed.

Swapping the arguments in the function call.

You store the function call divide(10, 2) in the variable result.

5fill in blank

hard

Fill all three blanks to call the function power with base 3 and exponent 4, store the result in res, and print it.

C

#include <stdio.h>

int power(int base, int exp) {
    int result = 1;
    for (int i = 0; i < exp; i++) {
        result *= base;
    }
    return result;
}

int main() {
    int [1] = [2];
    printf("%d\n", [3]);
    return 0;
}

Drag options to blanks, or click blank then click option'

Ares

Bpower(3, 4)

Dresult

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in declaration and print.

Calling the function with wrong arguments.

The variable res stores the result of power(3, 4), and we print res.

Practice

1. What does it mean to call a function in C?

easy

A. Execute the code inside the function by using its name and parentheses

B. Define the function with its code block

C. Declare the function prototype

D. Write comments about the function

Solution

1. Step 1: Understand function calling

   Calling a function means running the code inside it by using its name followed by parentheses.

2. Step 2: Differentiate from defining or declaring

   Defining or declaring a function is writing it, not running it. Calling is executing it.

3. Final Answer:

   Execute the code inside the function by using its name and parentheses -> Option A

4. Quick Check:

   Function call = run code by name() [OK]

Hint: Calling means running code by writing functionName() [OK]

Common Mistakes:

• Confusing calling with defining the function
• Thinking calling means declaring the function prototype
• Believing calling is writing comments

2. Which of the following is the correct syntax to call a function named printMessage in C?

easy

A. printMessage();

B. call printMessage;

C. printMessage;

D. function printMessage();

Solution

1. Step 1: Recall function call syntax

   In C, calling a function requires its name followed by parentheses and a semicolon.

2. Step 2: Check each option

   printMessage(); uses correct syntax: function name + parentheses + semicolon. Others are invalid syntax.

3. Final Answer:

   printMessage(); -> Option A

4. Quick Check:

   Function call syntax = name() [OK]

Hint: Function call always ends with (); [OK]

Common Mistakes:

• Omitting parentheses when calling
• Using keywords like 'call' which don't exist in C
• Missing semicolon at the end

3. What will be the output of this C program?

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

int main() {
    greet();
    return 0;
}

medium

A. Compilation error

B. Hello!

C. No output

D. greet()

Solution

1. Step 1: Understand function greet()

   The function greet() prints "Hello!" followed by a newline.

2. Step 2: Check main() function call

   Main calls greet(), so the program prints "Hello!" on the screen.

3. Final Answer:

   Hello! -> Option B

4. Quick Check:

   Calling greet() prints Hello! [OK]

Hint: Calling greet() prints its message exactly [OK]

Common Mistakes:

• Thinking function name prints output
• Assuming no output without explicit main print
• Confusing function call with declaration

4. Identify the error in this code snippet:

void sayHi() {
    printf("Hi!\n");
}

int main() {
    sayHi;
    return 0;
}

medium

A. printf statement is incorrect

B. Missing semicolon after sayHi

C. Function sayHi is not declared

D. Missing parentheses when calling sayHi

Solution

1. Step 1: Check function call syntax

   In main(), sayHi is written without parentheses, so it is not a function call.

2. Step 2: Correct function call

   To call sayHi, it must be written as sayHi(); with parentheses.

3. Final Answer:

   Missing parentheses when calling sayHi -> Option D

4. Quick Check:

   Function call needs () [OK]

Hint: Always use () to call a function [OK]

Common Mistakes:

• Omitting parentheses when calling functions
• Confusing function name with variable
• Assuming semicolon alone calls function

5. Given the function below, how would you call multiply to multiply 4 and 5 and print the result?

int multiply(int a, int b) {
    return a * b;
}

int main() {
    // Your code here
    return 0;
}

hard

A. int result = multiply(4, 5);

B. multiply(4, 5);

C. printf("%d", multiply(4, 5));

D. print(multiply(4, 5));

Solution

1. Step 1: Understand multiply function

   It returns the product of two integers.

2. Step 2: Call multiply and print result

   To show output, call multiply(4, 5) inside printf with %d format.

3. Final Answer:

   printf("%d", multiply(4, 5)); -> Option C

4. Quick Check:

   Use printf to display function return [OK]

Hint: Use printf to show returned value from function [OK]

Common Mistakes:

• Calling multiply without printing result
• Using print() instead of printf() in C
• Assigning result but not printing