Return values in C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to return the sum of two integers.

C

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

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

Aa - b

Ba + b

Ca * b

Da / b

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Forgetting to return a value.

The function should return the sum of a and b, so a + b is correct.

2fill in blank

medium

Complete the code to return the maximum of two integers.

C

int max(int x, int y) {
    if (x > y) {
        return [1];
    } else {
        return y;
    }
}

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

Ax

B0

Cy

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Returning the wrong variable inside the if block.

Returning a constant instead of a variable.

If x is greater than y, the function should return x.

3fill in blank

hard

Fix the error in the function to correctly return the length of a string.

C

#include <string.h>

int string_length(char *str) {
    int len = strlen(str);
    return [1];
}

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

A&len

Bstr

C*str

Dlen

Attempts:

3 left

💡 Hint

Common Mistakes

Returning the string pointer instead of the length.

Returning the address of the length variable.

The function calculates the length and stores it in len, so it should return len.

4fill in blank

hard

Fill both blanks to return the product of two numbers and print it.

C

#include <stdio.h>

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

int main() {
    int result = multiply(3, 4);
    printf("Product: %d\n", [2]);
    return 0;
}

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

Aa * b

Ba + b

Cresult

D3 * 4

Attempts:

3 left

💡 Hint

Common Mistakes

Returning sum instead of product.

Printing the wrong variable or expression.

The function should return the product a * b, and the printf should print the variable result which holds the product.

5fill in blank

hard

Fill all three blanks to create a function that returns the absolute value of an integer and use it in main.

C

#include <stdio.h>

int absolute([1] num) {
    if (num [2] 0) {
        return -num;
    } else {
        return num;
    }
}

int main() {
    int val = -10;
    int abs_val = absolute([3]);
    printf("Absolute value: %d\n", abs_val);
    return 0;
}

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

Aint

B<

Cval

Dfloat

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong data type for parameter.

Using wrong comparison operator.

Passing wrong variable to the function.

The function parameter should be an int. The condition checks if num < 0. In main, we pass val to the function.

Practice

1. What does the return statement do in a C function?

easy

A. It sends a value back to the place where the function was called.

B. It prints a value on the screen.

C. It declares a new variable inside the function.

D. It pauses the program execution.

Solution

1. Step 1: Understand the purpose of return

   The return statement sends a value from the function back to the caller.

2. Step 2: Differentiate from other actions

   Printing, declaring variables, or pausing are not what return does.

3. Final Answer:

   It sends a value back to the place where the function was called. -> Option A

4. Quick Check:

   Return sends value back [OK]

Hint: Return sends value back to caller, not print or pause [OK]

Common Mistakes:

• Thinking return prints output
• Confusing return with variable declaration
• Assuming return pauses program

2. Which of the following is the correct syntax for a function that returns an integer in C?

easy

A. int myFunction() { return 5; }

B. void myFunction() { return 5; }

C. int myFunction() { print(5); }

D. myFunction() int { return 5; }

Solution

1. Step 1: Check function return type and return statement

   The function declares int return type and returns an integer value 5.

2. Step 2: Identify incorrect options

   void myFunction() { return 5; } returns a value but declares void (no return). int myFunction() { print(5); } uses print which is invalid in C. myFunction() int { return 5; } has wrong syntax.

3. Final Answer:

   int myFunction() { return 5; } -> Option A

4. Quick Check:

   Return type matches returned value [OK]

Hint: Return type must match returned value type [OK]

Common Mistakes:

• Using void but returning a value
• Using print instead of return
• Wrong function syntax

3. What is the output of this C program?

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

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

medium

A. 34

B. 7

C. 0

D. Error

Solution

1. Step 1: Understand the add function

   The function adds two integers and returns their sum.

2. Step 2: Calculate the sum of 3 and 4

   3 + 4 equals 7, which is stored in result and printed.

3. Final Answer:

   7 -> Option B

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Add returns sum; printed result is sum [OK]

Common Mistakes:

• Concatenating numbers as strings
• Confusing return with print
• Expecting zero or error output

4. Identify the error in this C function:

int multiply(int x, int y) {
    int product = x * y;
}

medium

A. Variables x and y are not declared.

B. Incorrect multiplication operator.

C. Function name should be void.

D. Missing return statement to return the product.

Solution

1. Step 1: Check function return type and body

   The function declares it returns an int but does not return any value.

2. Step 2: Identify missing return statement

   It calculates product but never returns it, causing undefined behavior.

3. Final Answer:

   Missing return statement to return the product. -> Option D

4. Quick Check:

   Return missing in non-void function [OK]

Hint: Non-void functions must return a value [OK]

Common Mistakes:

• Forgetting to return value in non-void function
• Thinking multiplication operator is wrong
• Assuming variables are undeclared

5. You want to write a function that returns the maximum of three integers. Which of the following implementations correctly returns the maximum value?

hard

A. int maxOfThree(int a, int b, int c) {
if (a > b && a > c) return a;
else if (b > a && b > c) return b;
else return c;
}

B. int maxOfThree(int a, int b, int c) {
return a > b > c ? a : b > c ? b : c;
}

C. int maxOfThree(int a, int b, int c) {
int max = a;
if (b > max) max = b;
if (c > max) max = c;
return max;
}

D. int maxOfThree(int a, int b, int c) {
if (a > b) return a;
else if (b > c) return b;
else return c;
}

Solution

1. Step 1: Analyze int maxOfThree(int a, int b, int c) { if (a > b && a > c) return a; else if (b > a && b > c) return b; else return c; } logic

   This version correctly checks if b is greater than both a and c in the else-if condition, fixing the missing cases in the original version.

2. Step 2: Analyze int maxOfThree(int a, int b, int c) { int max = a; if (b > max) max = b; if (c > max) max = c; return max; } logic

   This compares all values step-by-step and returns the correct maximum.

3. Step 3: Analyze options C and D

   int maxOfThree(int a, int b, int c) { return a > b > c ? a : b > c ? b : c; } uses invalid chained comparison. int maxOfThree(int a, int b, int c) { if (a > b) return a; else if (b > c) return b; else return c; } misses some cases like when a is not greater than b but b is not greater than c.

4. Final Answer:

   int maxOfThree(int a, int b, int c) { int max = a; if (b > max) max = b; if (c > max) max = c; return max; } -> Option C

5. Quick Check:

   Stepwise max update returns correct max [OK]

Hint: Compare stepwise and return max variable [OK]

Common Mistakes:

• Using chained comparisons incorrectly
• Missing some comparison cases
• Returning before checking all values