Assignment operators in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign the value 10 to the variable x.

C++

int x [1] 10;

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

A=

B+=

C-=

D*=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+=' instead of '=' will add to the existing value instead of assigning.

Using '*=' or '-=' will perform multiplication or subtraction assignment, not simple assignment.

The assignment operator = assigns the value on the right to the variable on the left.

2fill in blank

medium

Complete the code to add 5 to the variable count using an assignment operator.

C++

count [1] 5;

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

A=

B*=

C-=

D+=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' will overwrite the value instead of adding.

Using '-=' or '*=' will subtract or multiply instead of adding.

The += operator adds the right value to the variable and assigns the result back to it.

3fill in blank

hard

Fix the error in the code to multiply total by 3 using an assignment operator.

C++

total [1] 3;

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

A+=

B=

C*=

D-=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' will overwrite the value instead of multiplying.

Using '+=' or '-=' will add or subtract instead of multiplying.

The *= operator multiplies the variable by the right value and assigns the result back.

4fill in blank

hard

Complete the code to subtract 4 from score and assign the result back.

C++

score [1] 4 ;

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

A-=

B+=

C;

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+=' will add instead of subtract.

Forgetting the semicolon causes a syntax error.

The -= operator subtracts and assigns, and the semicolon ends the statement.

5fill in blank

hard

Fill both blanks to divide value by 2 and assign the result back, then print it.

C++

value [1] 2 ;
std::cout [2] value << std::endl;

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

A/=

B;

C<<

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' instead of '/=' will overwrite without dividing.

Forgetting semicolons causes syntax errors.

Using '=' instead of '<<' for printing causes errors.

Use /= to divide and assign, end the first statement with ;, and use << to print.

Practice

1. Which of the following assignment operators adds the right value to the left variable and stores the result back in the left variable?

easy

A. +=

B. =

C. -=

D. *=

Solution

1. Step 1: Understand the meaning of +=

   The operator += adds the right side value to the left side variable and updates the variable with the new value.

2. Step 2: Compare with other operators

   = assigns a value, -= subtracts, and *= multiplies. Only += adds and assigns.

3. Final Answer:

   += -> Option A

4. Quick Check:

   Add and assign = += [OK]

Hint: Remember: += means add then assign [OK]

Common Mistakes:

• Confusing = with +=
• Thinking -= adds values
• Mixing *= with addition

2. Which of the following is the correct syntax to multiply variable x by 5 and store the result back in x?

easy

A. x =* 5;

B. x *= 5;

C. x = 5*;

D. x = 5 *;

Solution

1. Step 1: Identify the correct assignment operator syntax

   The operator to multiply and assign is *=, so x *= 5; is correct.

2. Step 2: Check other options for syntax errors

   x =* 5; and x = 5*; are invalid syntax. x = 5 *; is incomplete.

3. Final Answer:

   x *= 5; -> Option B

4. Quick Check:

   Multiply and assign = *= [OK]

Hint: Use operator before = for combined assignment [OK]

Common Mistakes:

• Placing * after = instead of before
• Leaving incomplete expressions
• Confusing with simple assignment =

3. What is the output of the following code?

int a = 10;
a += 5;
a -= 3;
std::cout << a;

medium

A. 12

B. 15

C. 8

D. 10

Solution

1. Step 1: Calculate a += 5;

   Starting with a = 10, adding 5 gives a = 15.

2. Step 2: Calculate a -= 3;

   Subtracting 3 from 15 gives a = 12.

3. Final Answer:

   12 -> Option A

4. Quick Check:

   10 + 5 - 3 = 12 [OK]

Hint: Apply each assignment step by step [OK]

Common Mistakes:

• Adding and subtracting in wrong order
• Confusing += and -= effects
• Ignoring the updated value after first operation

4. Identify the error in the following code snippet:

int x = 7;
x =+ 3;
std::cout << x;

medium

A. Syntax error due to incorrect operator

B. x will be 10

C. x will be 3

D. No error, output is 10

Solution

1. Step 1: Analyze x =+ 3;

   This is not the addition assignment +=. Instead, =+ means assign positive 3 to x.

2. Step 2: Determine the value of x after assignment

   x becomes 3, not 10, because =+ is just assignment with unary plus.

3. Final Answer:

   3 -> Option C

4. Quick Check:

   =+ is assignment, not addition [OK]

Hint: Watch for =+ vs += difference [OK]

Common Mistakes:

• Confusing =+ with += operator
• Expecting addition instead of assignment
• Assuming output is sum without checking syntax

5. Given int n = 20;, which code snippet correctly divides n by 4 and then subtracts 2 from the result, updating n accordingly?

hard

A. n = n - 2 / 4;

B. n -= 2; n /= 4;

C. n = (n - 2) / 4;

D. n /= 4; n -= 2;

Solution

1. Step 1: Understand the required operations order

   First divide n by 4, then subtract 2 from the result, updating n each time.

2. Step 2: Check each option

   n /= 4; n -= 2; does n /= 4; then n -= 2;, matching the requirement. n -= 2; n /= 4; reverses order. n = (n - 2) / 4; subtracts first due to parentheses (18 / 4 = 4). n = n - 2 / 4; subtracts incorrectly.

3. Step 3: Confirm correct update

   n /= 4; n -= 2; updates n stepwise as requested.

4. Final Answer:

   n /= 4; n -= 2; -> Option D

5. Quick Check:

   Divide then subtract = n /= 4; n -= 2; [OK]

Hint: Follow operation order exactly [OK]

Common Mistakes:

• Reversing operation order
• Misunderstanding combined expressions
• Incorrect operator precedence assumptions