Important Note: This is a basic CS101-style calculator intended purely for beginner learning. Not a portfolio-level project.
This is that basic calculator assignment everyone builds in their first C++ class. I'm uploading this cleaned-up version as a learning resource for beginners who need a reference implementation.
git clone https://github.com/jguida941/cpp-calculator-tutorial.git
cd cpp-calculator-tutorial
make
./build/calculatorThis repository exists to demonstrate clear documentation, clean code structure, and fundamental C++ practices, even for a simple beginner exercise. It serves as a reference implementation for students learning C++ fundamentals and addresses common compilation errors that beginners encounter.
- Four arithmetic operations: addition, subtraction, multiplication, division
- Natural expression input format (e.g.,
2 + 2) - Decimal number support
- Input validation and error handling
- Continuous operation mode with controlled exit
Note: This repository may contain additional PyQt or Jupyter Notebook files I'm currently working on. They are unrelated to the calculator project but safe to ignore or run if you're exploring my other work. The file tree below reflects the main calculator structure.
Cal/
├── README.md # This file
├── src/
│ └── calculator.cpp # Main source code
├── build/ # Compiled executables (generated)
├── examples/ # Example usage
└── Makefile # Build instructions
- C++ compiler (g++ or clang++)
- Make (optional, for using Makefile)
makeg++ -o build/calculator src/calculator.cppg++ -g -o build/calculator src/calculator.cpp./build/calculatorEnter expression (etc 2 + 2):
5 + 3
5 + 3 = 8
Do you wish to evaluate another expression? (Y/N)
y
Enter expression (etc 2 + 2):
10 / 2
10 / 2 = 5
Do you wish to evaluate another expression? (Y/N)
n
Program closing.
This project teaches you to avoid common C++ mistakes:
- Wrong main signature:
void main()→int main() - Wrong quotes for chars:
"Y"→'Y' - Semicolons after if:
if (condition);breaks logic flow - Stream operators:
<<for output,>>for input - Buffer issues: Not clearing input buffer causes unexpected behavior
- Input validation before processing
- Clear error messages
- Proper use of
stringstreamfor parsing - Handling edge cases (division by zero)
- Clean loop control with proper exit conditions
- Input/Output Stream Management - Proper use of
cin,cout, andgetline - String Parsing - Implementation with
stringstreamfor structured input - Control Flow - Conditional statements and loop structures
- Error Handling - Division by zero and invalid input validation
- Buffer Management - Clearing input stream for robust operation
- Project Organization - Structured directories with Makefile build system
-
String Streams: How
stringstreamhelps parse formatted inputstringstream ss(input); ss >> op1 >> operation >> op2; // Extracts values in order
-
Input Buffer Management: Why we need to clear the buffer
cin.ignore(numeric_limits<streamsize>::max(), '\n'); -
Error Checking: How to validate user input
if (!(ss >> op1 >> operation >> op2) || !ss.eof())
- Add support for exponentiation (^)
- Implement parentheses support
- Add memory functions (M+, M-, MR, MC)
- Create a history of calculations
- Add support for more complex expressions
Note: GitHub automatically renders this Mermaid diagram. If viewing locally, use a Mermaid-compatible markdown viewer.
flowchart TD
Start([Start Program]) --> Init[Initialize Variables:<br/>string input<br/>double op1, op2<br/>char operation<br/>char answer = Y]
Init --> LoopCheck{answer == 'Y'<br/>or 'y'?}
LoopCheck -->|No| End([End Program])
LoopCheck -->|Yes| GetInput[Prompt User:<br/>'Enter expression']
GetInput --> ReadLine[Read entire line<br/>using getline]
ReadLine --> CreateStream[Create stringstream<br/>from input]
CreateStream --> ParseInput{Parse:<br/>ss >> op1 >> operation >> op2}
ParseInput -->|Failed| ErrorInvalid[Display:<br/>'Error: Invalid input']
ErrorInvalid --> AskContinue
ParseInput -->|Success| CheckEOF{Check if<br/>stream is empty?}
CheckEOF -->|No| ErrorInvalid
CheckEOF -->|Yes| CheckOperator{Check<br/>operation type}
CheckOperator -->|'+'| Add[Calculate:<br/>result = op1 + op2]
CheckOperator -->|'-'| Sub[Calculate:<br/>result = op1 - op2]
CheckOperator -->|'*'| Mul[Calculate:<br/>result = op1 * op2]
CheckOperator -->|'/'| CheckDiv{op2 == 0?}
CheckOperator -->|Invalid| ErrorOp[Display:<br/>'Error: Invalid operator']
CheckDiv -->|Yes| ErrorDiv[Display:<br/>'Error: Division by zero']
CheckDiv -->|No| Div[Calculate:<br/>result = op1 / op2]
Add --> DisplayResult[Display:<br/>'op1 operator op2 = result']
Sub --> DisplayResult
Mul --> DisplayResult
Div --> DisplayResult
ErrorDiv --> AskContinue
ErrorOp --> AskContinue
DisplayResult --> AskContinue[Ask:<br/>'Evaluate another? Y/N']
AskContinue --> ReadAnswer[Read answer]
ReadAnswer --> ClearBuffer[Clear input buffer using cin.ignore]
ClearBuffer --> ValidateAnswer{answer is<br/>Y/y/N/n?}
ValidateAnswer -->|No| AskContinue
ValidateAnswer -->|Yes| CheckExit{answer is<br/>N or n?}
CheckExit -->|Yes| ShowClosing[Display:<br/>'Program closing']
CheckExit -->|No| LoopCheck
ShowClosing --> End
style Start fill:#e1f5e1
style End fill:#ffe1e1
style ErrorInvalid fill:#fff0e0
style ErrorOp fill:#fff0e0
style ErrorDiv fill:#fff0e0
style DisplayResult fill:#e0f0ff
The program follows this flow:
- Initialize variables and start loop
- Get expression from user
- Parse the input using stringstream
- Validate the input format
- Perform the calculation based on operator
- Display result
- Ask if user wants to continue
- Clear input buffer and repeat or exit
Educational use permitted. Students are encouraged to study and modify this code for learning purposes. Not intended for production use - this is purely a learning resource.
Educational reference implementation for C++ beginners