Assignment operators in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of compound assignment with addition

What is the output of this C code snippet?

C

int main() {
    int a = 5;
    a += 3;
    printf("%d", a);
    return 0;
}

A 8

B 3

C 0

D 5

💡 Hint

The += operator adds the right value to the left variable.

The operator 'a += 3' adds 3 to the current value of a (which is 5), so a becomes 8.

❓ Predict Output

intermediate

Result of bitwise AND assignment

What will be printed by this C program?

C

int main() {
    int x = 12;  // binary 1100
    x &= 5;      // binary 0101
    printf("%d", x);
    return 0;
}

A 12

B 5

C 4

D 1

💡 Hint

Bitwise AND compares each bit of two numbers and returns 1 only if both bits are 1.

12 (1100) & 5 (0101) = 0100 which is 4 in decimal.

❓ Predict Output

advanced

Output of chained assignment with multiplication

What is the output of this code?

C

int main() {
    int a = 2, b = 3, c = 4;
    a *= b *= c;
    printf("%d %d %d", a, b, c);
    return 0;
}

A 6 12 4

B 24 12 4

C 8 12 4

D 24 7 4

💡 Hint

Remember that assignment operators return the assigned value and evaluate right to left.

First, b *= c means b = 3 * 4 = 12. Then a *= b means a = 2 * 12 = 24. c remains 4.

❓ Predict Output

advanced

Effect of division assignment on float variable

What will this program print?

C

int main() {
    float f = 10.0f;
    f /= 4;
    printf("%.2f", f);
    return 0;
}

A 2.50

B 2.00

C 2.40

D 2.45

💡 Hint

Division assignment divides the variable by the right value and stores the result.

10.0 divided by 4 is 2.5, printed with two decimals as 2.50.

❓ Predict Output

expert

Final value after multiple compound assignments

What is the final value of variable x after running this code?

C

int main() {
    int x = 1;
    x += 2;
    x *= 3;
    x -= 4;
    x /= 2;
    printf("%d", x);
    return 0;
}

A 3

B 0

C 1

D 2

💡 Hint

Apply each assignment operator step by step in order.

x starts at 1, then x += 2 → 3, x *= 3 → 9, x -= 4 → 5, x /= 2 → 2 (integer division).

Practice

1. Which of the following assignment operators adds the right operand to the left operand and then assigns the result to the left operand?

easy

A. -=

B. +=

C. *=

D. /=

Solution

1. Step 1: Understand the meaning of += operator

   The operator += adds the value on the right to the variable on the left and stores the result back in the left variable.

2. Step 2: Compare with other operators

   Other operators like -= subtract, *= multiply, and /= divide, so they do not add.

3. Final Answer:

   += -> Option B

4. Quick Check:

   += means add and assign [OK]

Hint: Remember '+=' means add then assign to left variable [OK]

Common Mistakes:

• Confusing '+=' with '=' which just assigns
• Mixing '+=' with '-=' or '*='
• Thinking '+=' only adds without assignment

2. Which of the following is the correct syntax using the compound assignment operator to multiply variable x by 5 and assign the result back to x?

easy

A. x = x *5;

B. x =* 5;

C. x = *5;

D. x *= 5;

Solution

1. Step 1: Identify correct compound assignment syntax

   The correct syntax for multiplying and assigning is 'x *= 5;'. It combines multiplication and assignment.

2. Step 2: Check other options for syntax errors

   x =* 5; 'x =* 5;' is invalid syntax. x = *5; 'x = *5;' is invalid because '*5' is not a valid expression. x = x *5; 'x = x *5;' is correct but not a compound assignment operator.

3. Final Answer:

   x *= 5; -> Option D

4. Quick Check:

   '*=' is multiply and assign operator [OK]

Hint: Use '*=' to multiply and assign in one step [OK]

Common Mistakes:

• Writing '=*' instead of '*='
• Forgetting space or semicolon
• Using 'x = *5;' which is invalid

3. What is the output of the following code?

int a = 10;
a += 5;
a -= 3;
printf("%d", a);

medium

A. 8

B. 15

C. 12

D. 10

Solution

1. Step 1: Calculate after first operation 'a += 5;'

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

2. Step 2: Calculate after second operation 'a -= 3;'

   Subtracting 3 from 15 gives a = 12.

3. Final Answer:

   12 -> Option C

4. Quick Check:

   10 + 5 - 3 = 12 [OK]

Hint: Apply each operator step-by-step to track value [OK]

Common Mistakes:

• Adding and subtracting in wrong order
• Confusing '+=' and '-=' effects
• Ignoring initial value of variable

4. Identify the error in the following code snippet:

int x = 7;
x +== 3;
printf("%d", x);

medium

A. Syntax error due to '+==' operator

B. Runtime error due to invalid operation

C. No error, output is 10

D. Logical error, output is wrong

Solution

1. Step 1: Check the operator '+==' in the code

   The operator '+==' does not exist in C. The correct operator for addition assignment is '+='.

2. Step 2: Understand the effect of invalid operator

   Using '+==' causes a syntax error and the code will not compile.

3. Final Answer:

   Syntax error due to '+==' operator -> Option A

4. Quick Check:

   Invalid operator '+==' causes syntax error [OK]

Hint: Use '+=' not '+==' for addition assignment [OK]

Common Mistakes:

• Typing '+==' instead of '+='
• Assuming '+==' works like '=='
• Ignoring compiler error messages

5. Given the code below, what is the final value of result?

int result = 20;
result /= 4;
result *= 3;
result %= 5;
result += 2;
printf("%d", result);

hard

A. 2

B. 3

C. 4

D. 1

Solution

1. Step 1: Perform division assignment 'result /= 4;'

   Starting with result = 20, dividing by 4 gives result = 5.

2. Step 2: Perform multiplication assignment 'result *= 3;'

   Multiplying 5 by 3 gives result = 15.

3. Step 3: Perform modulus assignment 'result %= 5;'

   15 modulo 5 is 0, so result = 0.

4. Step 4: Perform addition assignment 'result += 2;'

   Adding 2 to 0 gives result = 2.

5. Final Answer:

   2 -> Option A

6. Quick Check:

   20/4=5, 5*3=15, 15%5=0, 0+2=2 [OK]

Hint: Apply each operator in order carefully [OK]

Common Mistakes:

• Skipping modulus step or calculating it wrong
• Mixing up order of operations
• Forgetting that %= gives remainder