Why functions are needed - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a function named greet.

C

void [1]() {
    printf("Hello!\n");
}

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

Aprint

Bmain

Cgreet

Dhello

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'main' instead of the function name.

Using 'print' which is not a valid function name in C.

Using 'hello' which is not the intended function name.

The function name should be greet to match the definition.

2fill in blank

medium

Complete the code to call the function greet inside main.

C

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

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

Agreet

Bhello

Cprint

Dmain

Attempts:

3 left

💡 Hint

Common Mistakes

Calling 'print()' which is not defined.

Calling 'hello()' which is not defined.

Calling 'main()' inside main causes recursion.

To call the function defined as greet, use greet();.

3fill in blank

hard

Fix the error in the function definition by completing the return type.

C

[1] greet() {
    printf("Hello!\n");
}

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

Avoid

Bint

Cchar

Dfloat

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'int' without a return statement causes warnings.

Using 'char' or 'float' which are incorrect for this function.

The function does not return a value, so its return type should be void.

4fill in blank

hard

Fill both blanks to create a function that adds two numbers and returns the result.

C

[1] add(int a, int b) {
    return a [2] b;
}

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

Aint

B+

C-

Dvoid

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'void' as return type when a value is returned.

Using '-' instead of '+' for addition.

The function returns an integer, so the return type is int. To add two numbers, use the + operator.

5fill in blank

hard

Fill all three blanks to create a function that checks if a number is even and returns 1 if true, else 0.

C

[1] is_even(int num) {
    if (num [2] 2 == 0) {
        return [3];
    } else {
        return 0;
    }
}

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

Aint

B%

C1

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '%' to check remainder.

Returning 0 instead of 1 when number is even.

The function returns an integer, so use int. To check if a number is even, use the modulus operator % to get the remainder. If remainder is 0, return 1 to indicate true.

Practice

1. Why do we use functions in C programming?

easy

A. To avoid using variables

B. To make the program run faster

C. To write code without any syntax

D. To break code into smaller, manageable parts

Solution

1. Step 1: Understand the purpose of functions

   Functions help organize code by dividing it into smaller parts.

2. Step 2: Compare options with this purpose

   Only To break code into smaller, manageable parts matches the idea of breaking code into manageable parts.

3. Final Answer:

   To break code into smaller, manageable parts -> Option D

4. Quick Check:

   Functions organize code = C [OK]

Hint: Functions split code into pieces for clarity [OK]

Common Mistakes:

• Thinking functions make code run faster
• Believing functions remove the need for variables
• Assuming functions remove syntax rules

2. Which of the following is the correct way to declare a function in C?

easy

A. add int a, int b;

B. int add(int a, int b);

C. def add(a, b):

D. function add(a, b) {}

Solution

1. Step 1: Recall C function declaration syntax

   In C, functions are declared with return type, name, and parameters in parentheses.

2. Step 2: Match options to C syntax

   int add(int a, int b); matches C syntax; others are from other languages or incorrect.

3. Final Answer:

   int add(int a, int b); -> Option B

4. Quick Check:

   C function declaration = D [OK]

Hint: C functions need return type and parameter types [OK]

Common Mistakes:

• Using Python or JavaScript syntax in C
• Omitting return type in declaration
• Writing parameters without types

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

int add(int x, int y) { return x + y; }
int main() {
  int result = add(3, 4);
  printf("%d", result);
  return 0;
}

medium

A. 0

B. 34

C. 7

D. Error

Solution

1. Step 1: Understand the add function

   The function adds two integers and returns their sum.

2. Step 2: Calculate add(3, 4)

   3 + 4 equals 7, so result is 7.

3. Final Answer:

   7 -> Option C

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Add function returns sum; 3 + 4 = 7 [OK]

Common Mistakes:

• Thinking it prints '34' as string concatenation
• Assuming default return 0
• Expecting a syntax error

4. Identify the error in this C function usage:

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

int main() {
  int result = multiply(5);
  printf("%d", result);
  return 0;
}

medium

A. Function multiply is called with wrong number of arguments

B. Function multiply has no return statement

C. printf is missing a format specifier

D. Variable result is not declared

Solution

1. Step 1: Check function call arguments

   multiply expects 2 arguments but is called with 1.

2. Step 2: Verify other parts

   Function has return, printf has correct format, result declared.

3. Final Answer:

   Function multiply is called with wrong number of arguments -> Option A

4. Quick Check:

   Argument count mismatch = A [OK]

Hint: Count function arguments carefully [OK]

Common Mistakes:

• Ignoring argument count mismatch
• Thinking missing return causes error here
• Assuming printf format is wrong

5. You want to reuse a piece of code that calculates the area of a rectangle multiple times in your program. What is the best way to do this in C?

hard

A. Use a function that takes length and width and returns the area

B. Write the area calculation code repeatedly wherever needed

C. Copy and paste the code inside main() multiple times

D. Use global variables to store length and width and calculate area once

Solution

1. Step 1: Understand code reuse benefits

   Functions let you write code once and reuse it easily.

2. Step 2: Identify best reuse method

   Using a function with parameters for length and width is best practice.

3. Final Answer:

   Use a function that takes length and width and returns the area -> Option A

4. Quick Check:

   Functions enable code reuse = B [OK]

Hint: Use functions to avoid repeating code [OK]

Common Mistakes:

• Repeating code instead of using functions
• Using global variables unnecessarily
• Copy-pasting code causing maintenance issues