Arithmetic operators in C++ - Step-by-Step Execution

Concept Flow - Arithmetic operators

Start

↓

Read operands

↓

Choose operator: +, -, *, /, %

↓

Perform calculation

↓

Store/Display result

↓

End

The program starts by reading two numbers, then chooses an arithmetic operator to perform the calculation, and finally shows the result.

Execution Sample

C++

int a = 10;
int b = 3;
int sum = a + b;
int diff = a - b;
int prod = a * b;
int quot = a / b;
int mod = a % b;

This code calculates sum, difference, product, quotient, and remainder of two integers.

Execution Table

Step	Operation	Operands	Result	Explanation
1	Addition	10 + 3	13	Adds a and b, stores in sum
2	Subtraction	10 - 3	7	Subtracts b from a, stores in diff
3	Multiplication	10 * 3	30	Multiplies a and b, stores in prod
4	Division	10 / 3	3	Divides a by b (integer division), stores in quot
5	Modulo	10 % 3	1	Remainder of a divided by b, stores in mod
6	End	-	-	All operations done

💡 All arithmetic operations completed and results stored.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5
a	10	10	10	10	10	10
b	3	3	3	3	3	3
sum	undefined	13	13	13	13	13
diff	undefined	undefined	7	7	7	7
prod	undefined	undefined	undefined	30	30	30
quot	undefined	undefined	undefined	undefined	3	3
mod	undefined	undefined	undefined	undefined	undefined	1

Key Moments - 3 Insights

Why does division 10 / 3 give 3 instead of 3.333?

Because both a and b are integers, C++ does integer division which discards the decimal part. See step 4 in execution_table.

What does the modulo operator (%) do?

It gives the remainder after division. For 10 % 3, the remainder is 1 as shown in step 5.

Are the original variables a and b changed by these operations?

No, a and b keep their original values throughout, only new variables store results. See variable_tracker.

Visual Quiz - 3 Questions

Look at the execution_table, what is the result of the multiplication at step 3?

A 30

B 13

C 7

D 3

💡 Hint

Check the 'Result' column for step 3 in execution_table.

At which step does the modulo operation happen?

A Step 2

B Step 5

C Step 4

D Step 1

💡 Hint

Look for '%' operator in the 'Operation' column in execution_table.

If variable b was 4 instead of 3, what would be the new result of 10 % b?

A 1

B 0

C 2

D 3

💡 Hint

Modulo gives remainder: 10 divided by 4 leaves remainder 2.

Concept Snapshot

Arithmetic operators in C++:
+ addition
- subtraction
* multiplication
/ division (integer if both operands int)
% modulo (remainder)
Operands must be numbers; integer division truncates decimals.

Full Transcript

This example shows how arithmetic operators work in C++. We start with two integers a=10 and b=3. We add them to get 13, subtract to get 7, multiply to get 30, divide to get 3 (integer division), and find remainder 1 using modulo. Variables a and b remain unchanged. Each step performs one operation and stores the result in a new variable. Integer division discards decimals. Modulo gives the remainder after division.

Practice

1. Which arithmetic operator in C++ is used to find the remainder of a division?

easy

A. -

B. /

C. %

D. *

Solution

1. Step 1: Understand the meaning of each operator

   The operator % returns the remainder after division, while / returns the quotient.

2. Step 2: Identify the operator for remainder

   Since remainder is asked, the correct operator is %.

3. Final Answer:

   % -> Option C

4. Quick Check:

   Remainder operator = % [OK]

Hint: Remainder uses % symbol, not division / [OK]

Common Mistakes:

• Confusing / with %
• Using * for remainder
• Using - for remainder

2. Which of the following is the correct syntax to multiply two integers a and b in C++?

easy

A. a * b;

B. a x b;

C. a multiply b;

D. a . b;

Solution

1. Step 1: Recall multiplication operator syntax

   In C++, multiplication uses the asterisk symbol * between operands.

2. Step 2: Check each option

   Only a * b; uses the correct operator and syntax.

3. Final Answer:

   a * b; -> Option A

4. Quick Check:

   Multiplication operator = * [OK]

Hint: Use * for multiplication, not words or symbols [OK]

Common Mistakes:

• Using x instead of *
• Writing multiply as word
• Using dot operator for math

3. What is the output of the following C++ code?

int a = 10, b = 3;
std::cout << a / b << std::endl;

medium

A. 3.33333

B. 3

C. 4

D. Error

Solution

1. Step 1: Understand integer division in C++

   Both a and b are integers, so division truncates decimals.

2. Step 2: Calculate integer division result

   10 divided by 3 is 3.333..., but integer division returns 3.

3. Final Answer:

   3 -> Option B

4. Quick Check:

   Integer division truncates decimals = 3 [OK]

Hint: Integer division drops decimals, result is integer [OK]

Common Mistakes:

• Expecting decimal result
• Using floating-point division without casting
• Thinking output is error

4. Identify the error in this C++ code snippet:

int x = 5;
int y = 2;
int z = x / y.0;
std::cout << z << std::endl;

medium

A. Syntax error due to decimal point in divisor

B. Using floating-point literal with integer division

C. Incorrect variable declaration

D. Missing semicolon

Solution

1. Step 1: Analyze the divisor y.0

   The expression y.0 is invalid syntax in C++ because variables cannot have decimal points.

2. Step 2: Identify the syntax error

   The decimal point after y causes a syntax error; correct would be y * 1.0 or static_cast<double>(y).

3. Final Answer:

   Syntax error due to decimal point in divisor -> Option A

4. Quick Check:

   Variable names cannot have decimal points [OK]

Hint: Variable names can't have dots; causes syntax error [OK]

Common Mistakes:

• Thinking y.0 is valid float
• Ignoring syntax error
• Confusing variable and literal

5. Given int a = 7, b = 4;, which expression correctly calculates the average as a floating-point number in C++?

hard

A. a / b + 2

B. (a + b) / 2

C. a + b / 2

D. (a + b) / 2.0

Solution

1. Step 1: Understand integer vs floating-point division

   Using 2 divides integers, truncating decimals. Using 2.0 forces floating-point division.

2. Step 2: Evaluate each option

   (a + b) / 2 does integer division, result 5. (a + b) / 2.0 divides by 2.0, giving 5.5 as float. Options C and D do not calculate average correctly.

3. Final Answer:

   (a + b) / 2.0 -> Option D

4. Quick Check:

   Use floating-point divisor for decimal average [OK]

Hint: Divide by 2.0 to get decimal average, not integer [OK]

Common Mistakes:

• Using integer 2 causing truncation
• Wrong operator precedence
• Misinterpreting average formula