diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..9c73654
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,12 @@
+# Build artifacts
+obj/
+calculator
+
+# macOS
+.DS_Store
+
+# Editor
+.vscode/
+.idea/
+
+
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..4395926
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,41 @@
+# Makefile for Scientific Calculator
+
+CXX = g++
+CXXFLAGS = -std=c++17 -Wall -Wextra -O2
+TARGET = calculator
+SRCDIR = src
+OBJDIR = obj
+
+# Source files
+SOURCES = $(wildcard $(SRCDIR)/*.cpp)
+OBJECTS = $(SOURCES:$(SRCDIR)/%.cpp=$(OBJDIR)/%.o)
+
+# Default target
+all: $(TARGET)
+
+# Create object directory if it doesn't exist
+$(OBJDIR):
+	mkdir -p $(OBJDIR)
+
+# Link object files to create executable
+$(TARGET): $(OBJECTS) | $(OBJDIR)
+	$(CXX) $(OBJECTS) -o $(TARGET) $(LDFLAGS)
+	@echo "Build complete: $(TARGET)"
+
+# Compile source files to object files
+$(OBJDIR)/%.o: $(SRCDIR)/%.cpp | $(OBJDIR)
+	$(CXX) $(CXXFLAGS) -c $< -o $@
+
+# Clean build artifacts
+clean:
+	rm -rf $(OBJDIR) $(TARGET)
+	@echo "Clean complete"
+
+# Run the calculator in interactive mode
+run: $(TARGET)
+	./$(TARGET)
+
+# Phony targets
+.PHONY: all clean run
+
+
diff --git a/src/Calculator.cpp b/src/Calculator.cpp
new file mode 100644
index 0000000..3968740
--- /dev/null
+++ b/src/Calculator.cpp
@@ -0,0 +1,21 @@
+// Calculator.cpp
+
+#include "Calculator.h"
+
+namespace sci_calc {
+
+Calculator::Calculator() : parser_(), evaluator_() {
+}
+
+double Calculator::calculate(const std::string &expression) {
+    if (expression.empty()) {
+        throw InvalidInputException("Empty expression");
+    }
+
+    std::vector<Token> postfixTokens = parser_.parseToPostfix(expression);
+    return evaluator_.evaluate(postfixTokens);
+}
+
+} // namespace sci_calc
+
+
diff --git a/src/Calculator.h b/src/Calculator.h
new file mode 100644
index 0000000..a5c652e
--- /dev/null
+++ b/src/Calculator.h
@@ -0,0 +1,27 @@
+// Calculator.h
+// Main calculator class that coordinates parsing and evaluation
+
+#pragma once
+
+#include "ExpressionParser.h"
+#include "ExpressionEvaluator.h"
+#include "Exceptions.h"
+
+#include <string>
+
+namespace sci_calc {
+
+class Calculator {
+public:
+    Calculator();
+    
+    double calculate(const std::string &expression);
+
+private:
+    ExpressionParser parser_;
+    ExpressionEvaluator evaluator_;
+};
+
+} // namespace sci_calc
+
+
diff --git a/src/Exceptions.h b/src/Exceptions.h
new file mode 100644
index 0000000..4775d7c
--- /dev/null
+++ b/src/Exceptions.h
@@ -0,0 +1,31 @@
+// Exceptions.h
+// Scientific Calculator custom exception hierarchy
+
+#pragma once
+
+#include <stdexcept>
+#include <string>
+
+namespace sci_calc {
+
+class CalculatorException : public std::runtime_error {
+public:
+    explicit CalculatorException(const std::string &message)
+        : std::runtime_error(message) {}
+};
+
+class InvalidInputException : public CalculatorException {
+public:
+    explicit InvalidInputException(const std::string &message)
+        : CalculatorException(message) {}
+};
+
+class MathDomainException : public CalculatorException {
+public:
+    explicit MathDomainException(const std::string &message)
+        : CalculatorException(message) {}
+};
+
+} // namespace sci_calc
+
+
diff --git a/src/ExpressionEvaluator.cpp b/src/ExpressionEvaluator.cpp
new file mode 100644
index 0000000..7c378e1
--- /dev/null
+++ b/src/ExpressionEvaluator.cpp
@@ -0,0 +1,158 @@
+// ExpressionEvaluator.cpp
+
+#include "ExpressionEvaluator.h"
+
+#include <stdexcept>
+
+namespace sci_calc {
+
+double ExpressionEvaluator::evaluate(const std::vector<Token> &postfixTokens) const {
+    std::stack<double> stack;
+
+    for (const auto &token : postfixTokens) {
+        switch (token.type) {
+            case TokenType::Number:
+            case TokenType::Constant:
+                stack.push(token.value);
+                break;
+
+            case TokenType::Operator: {
+                if (stack.size() < 1) {
+                    throw InvalidInputException("Insufficient operands for operator: " + token.text);
+                }
+
+                if (token.text == "neg" || token.text == "pos") {
+                    double a = stack.top();
+                    stack.pop();
+                    stack.push(applyUnaryOperator(token.text, a));
+                } else {
+                    if (stack.size() < 2) {
+                        throw InvalidInputException("Insufficient operands for binary operator: " + token.text);
+                    }
+                    double b = stack.top();
+                    stack.pop();
+                    double a = stack.top();
+                    stack.pop();
+                    stack.push(applyOperator(token.text, a, b));
+                }
+                break;
+            }
+
+            case TokenType::Function: {
+                if (stack.empty()) {
+                    throw InvalidInputException("Insufficient operands for function: " + token.text);
+                }
+                double arg = stack.top();
+                stack.pop();
+                stack.push(applyFunction(token.text, arg));
+                break;
+            }
+
+            default:
+                throw InvalidInputException("Unexpected token type in postfix expression");
+        }
+    }
+
+    if (stack.size() != 1) {
+        throw InvalidInputException("Invalid expression: stack contains " + 
+                                   std::to_string(stack.size()) + " values");
+    }
+
+    return stack.top();
+}
+
+double ExpressionEvaluator::applyOperator(const std::string &op, double a, double b) const {
+    if (op == "+") {
+        return a + b;
+    } else if (op == "-") {
+        return a - b;
+    } else if (op == "*") {
+        return a * b;
+    } else if (op == "/") {
+        if (std::abs(b) < 1e-10) {
+            throw MathDomainException("Division by zero");
+        }
+        return a / b;
+    } else if (op == "%") {
+        if (std::abs(b) < 1e-10) {
+            throw MathDomainException("Modulo by zero");
+        }
+        return std::fmod(a, b);
+    } else if (op == "^") {
+        if (a < 0 && std::fmod(b, 1.0) != 0.0) {
+            throw MathDomainException("Cannot raise negative number to non-integer power");
+        }
+        double result = std::pow(a, b);
+        if (std::isnan(result) || std::isinf(result)) {
+            throw MathDomainException("Power operation resulted in invalid value");
+        }
+        return result;
+    } else {
+        throw InvalidInputException("Unknown operator: " + op);
+    }
+}
+
+double ExpressionEvaluator::applyUnaryOperator(const std::string &op, double a) const {
+    if (op == "neg") {
+        return -a;
+    } else if (op == "pos") {
+        return a;
+    } else {
+        throw InvalidInputException("Unknown unary operator: " + op);
+    }
+}
+
+double ExpressionEvaluator::applyFunction(const std::string &func, double arg) const {
+    if (func == "sin") {
+        return std::sin(arg);
+    } else if (func == "cos") {
+        return std::cos(arg);
+    } else if (func == "tan") {
+        double result = std::tan(arg);
+        if (std::isinf(result) || std::isnan(result)) {
+            throw MathDomainException("Tangent is undefined for the given angle");
+        }
+        return result;
+    } else if (func == "asin") {
+        if (arg < -1.0 || arg > 1.0) {
+            throw MathDomainException("Arcsin argument must be in range [-1, 1]");
+        }
+        return std::asin(arg);
+    } else if (func == "acos") {
+        if (arg < -1.0 || arg > 1.0) {
+            throw MathDomainException("Arccos argument must be in range [-1, 1]");
+        }
+        return std::acos(arg);
+    } else if (func == "atan") {
+        return std::atan(arg);
+    } else if (func == "log") {
+        if (arg <= 0.0) {
+            throw MathDomainException("Logarithm argument must be positive");
+        }
+        return std::log10(arg);
+    } else if (func == "ln") {
+        if (arg <= 0.0) {
+            throw MathDomainException("Natural logarithm argument must be positive");
+        }
+        return std::log(arg);
+    } else if (func == "sqrt") {
+        if (arg < 0.0) {
+            throw MathDomainException("Square root of negative number is not a real number");
+        }
+        return std::sqrt(arg);
+    } else if (func == "exp") {
+        double result = std::exp(arg);
+        if (std::isinf(result)) {
+            throw MathDomainException("Exponential overflow");
+        }
+        return result;
+    } else if (func == "abs") {
+        return std::abs(arg);
+    } else {
+        throw InvalidInputException("Unknown function: " + func);
+    }
+}
+
+} // namespace sci_calc
+
+
diff --git a/src/ExpressionEvaluator.h b/src/ExpressionEvaluator.h
new file mode 100644
index 0000000..ea8ea6b
--- /dev/null
+++ b/src/ExpressionEvaluator.h
@@ -0,0 +1,27 @@
+// ExpressionEvaluator.h
+// Evaluates postfix expression tokens and performs mathematical operations
+
+#pragma once
+
+#include "ExpressionParser.h"
+#include "Exceptions.h"
+
+#include <stack>
+#include <vector>
+#include <cmath>
+
+namespace sci_calc {
+
+class ExpressionEvaluator {
+public:
+    double evaluate(const std::vector<Token> &postfixTokens) const;
+
+private:
+    double applyOperator(const std::string &op, double a, double b) const;
+    double applyUnaryOperator(const std::string &op, double a) const;
+    double applyFunction(const std::string &func, double arg) const;
+};
+
+} // namespace sci_calc
+
+
diff --git a/src/ExpressionParser.cpp b/src/ExpressionParser.cpp
new file mode 100644
index 0000000..134331b
--- /dev/null
+++ b/src/ExpressionParser.cpp
@@ -0,0 +1,270 @@
+// ExpressionParser.cpp
+
+#include "ExpressionParser.h"
+
+#include <algorithm>
+#include <cctype>
+#include <stack>
+
+namespace sci_calc {
+
+namespace {
+
+std::string toLower(std::string text) {
+    std::transform(text.begin(), text.end(), text.begin(), [](unsigned char ch) {
+        return static_cast<char>(std::tolower(ch));
+    });
+    return text;
+}
+
+} // namespace
+
+ExpressionParser::ExpressionParser() {
+    operators_.emplace("+", OperatorInfo{2, false, 2});
+    operators_.emplace("-", OperatorInfo{2, false, 2});
+    operators_.emplace("*", OperatorInfo{3, false, 2});
+    operators_.emplace("/", OperatorInfo{3, false, 2});
+    operators_.emplace("%", OperatorInfo{3, false, 2});
+    operators_.emplace("^", OperatorInfo{4, true, 2});
+    operators_.emplace("neg", OperatorInfo{5, true, 1});
+
+    constants_.emplace("pi", 3.14159265358979323846);
+    constants_.emplace("e", 2.71828182845904523536);
+}
+
+std::vector<Token> ExpressionParser::parseToPostfix(const std::string &expression) const {
+    std::vector<Token> output;
+    std::stack<Token> stack;
+
+    std::size_t i = 0;
+    while (i < expression.size()) {
+        char ch = expression[i];
+
+        if (std::isspace(static_cast<unsigned char>(ch))) {
+            ++i;
+            continue;
+        }
+
+        if (std::isdigit(static_cast<unsigned char>(ch)) ||
+            (ch == '.' && i + 1 < expression.size() &&
+             std::isdigit(static_cast<unsigned char>(expression[i + 1])))) {
+            output.push_back(parseNumber(expression, i));
+            continue;
+        }
+
+        if (isIdentifierChar(ch)) {
+            Token identifier = parseIdentifier(expression, i);
+            if (identifier.type == TokenType::Constant) {
+                output.push_back(identifier);
+            } else {
+                stack.push(identifier);
+            }
+            continue;
+        }
+
+        if (ch == ',') {
+            // Function argument separator is unsupported (all functions are unary)
+            throw InvalidInputException("Unexpected ',' in expression: multiple arguments not supported");
+        }
+
+        if (ch == '(') {
+            stack.push(Token{TokenType::OpenParen, "(", 0.0});
+            ++i;
+            continue;
+        }
+
+        if (ch == ')') {
+            ++i;
+            bool foundOpenParen = false;
+            while (!stack.empty()) {
+                Token top = stack.top();
+                stack.pop();
+                if (top.type == TokenType::OpenParen) {
+                    foundOpenParen = true;
+                    break;
+                }
+                output.push_back(top);
+            }
+
+            if (!foundOpenParen) {
+                throw InvalidInputException("Unmatched ')' in expression");
+            }
+
+            if (!stack.empty() && stack.top().type == TokenType::Function) {
+                output.push_back(stack.top());
+                stack.pop();
+            }
+            continue;
+        }
+
+        // Operators
+        Token opToken = parseOperator(expression, i, output);
+
+        while (!stack.empty()) {
+            const Token &top = stack.top();
+            if (top.type != TokenType::Operator) {
+                break;
+            }
+
+            const auto &currentInfo = operators_.at(opToken.text);
+            const auto &topInfo = operators_.at(top.text);
+
+            bool shouldPop = (!currentInfo.rightAssociative && currentInfo.precedence <= topInfo.precedence) ||
+                             (currentInfo.rightAssociative && currentInfo.precedence < topInfo.precedence);
+
+            if (!shouldPop) {
+                break;
+            }
+
+            output.push_back(top);
+            stack.pop();
+        }
+
+        stack.push(opToken);
+    }
+
+    while (!stack.empty()) {
+        Token top = stack.top();
+        stack.pop();
+        if (top.type == TokenType::OpenParen || top.type == TokenType::CloseParen) {
+            throw InvalidInputException("Unmatched '(' in expression");
+        }
+        output.push_back(top);
+    }
+
+    return output;
+}
+
+bool ExpressionParser::isIdentifierChar(char ch) {
+    return std::isalpha(static_cast<unsigned char>(ch)) || ch == '_';
+}
+
+Token ExpressionParser::parseNumber(const std::string &expression, std::size_t &index) const {
+    std::size_t start = index;
+    bool hasDecimalPoint = false;
+
+    while (index < expression.size()) {
+        char ch = expression[index];
+        if (std::isdigit(static_cast<unsigned char>(ch))) {
+            ++index;
+            continue;
+        }
+        if (ch == '.' && !hasDecimalPoint) {
+            hasDecimalPoint = true;
+            ++index;
+            continue;
+        }
+        if ((ch == 'e' || ch == 'E') && index + 1 < expression.size()) {
+            std::size_t expIndex = index + 1;
+            if (expression[expIndex] == '+' || expression[expIndex] == '-') {
+                ++expIndex;
+            }
+            if (expIndex >= expression.size() ||
+                !std::isdigit(static_cast<unsigned char>(expression[expIndex]))) {
+                throw InvalidInputException("Malformed exponent in number literal");
+            }
+            index = expIndex + 1;
+            while (index < expression.size() &&
+                   std::isdigit(static_cast<unsigned char>(expression[index]))) {
+                ++index;
+            }
+            break;
+        }
+        break;
+    }
+
+    const std::string literal = expression.substr(start, index - start);
+    try {
+        double value = std::stod(literal);
+        return Token{TokenType::Number, literal, value};
+    } catch (const std::exception &) {
+        throw InvalidInputException("Unable to parse number literal: " + literal);
+    }
+}
+
+Token ExpressionParser::parseIdentifier(const std::string &expression, std::size_t &index) const {
+    std::size_t start = index;
+    while (index < expression.size() &&
+           (isIdentifierChar(expression[index]) ||
+            std::isdigit(static_cast<unsigned char>(expression[index])))) {
+        ++index;
+    }
+
+    std::string identifier = expression.substr(start, index - start);
+    std::string lower = toLower(identifier);
+
+    auto constantIt = constants_.find(lower);
+    if (constantIt != constants_.end()) {
+        return Token{TokenType::Constant, lower, constantIt->second};
+    }
+
+    static const std::unordered_map<std::string, int> functions = {
+        {"sin", 1}, {"cos", 1}, {"tan", 1}, {"asin", 1}, {"acos", 1}, {"atan", 1},
+        {"log", 1}, {"ln", 1}, {"sqrt", 1}, {"exp", 1}, {"abs", 1}};
+
+    if (functions.find(lower) != functions.end()) {
+        return Token{TokenType::Function, lower, 0.0};
+    }
+
+    throw InvalidInputException("Unknown identifier: " + identifier);
+}
+
+bool ExpressionParser::isUnaryOperator(const std::string &expression, std::size_t index,
+                                       const std::vector<Token> &output) const {
+    if (index == 0) {
+        return true;
+    }
+
+    std::size_t prevIndex = index;
+    while (prevIndex > 0) {
+        char prevChar = expression[prevIndex - 1];
+        if (std::isspace(static_cast<unsigned char>(prevChar))) {
+            --prevIndex;
+            continue;
+        }
+        break;
+    }
+
+    if (prevIndex == 0) {
+        return true;
+    }
+
+    char prevChar = expression[prevIndex - 1];
+
+    if (prevChar == '(' || prevChar == ',' || operators_.count(std::string(1, prevChar)) > 0) {
+        return true;
+    }
+
+    if (!output.empty()) {
+        Token lastToken = output.back();
+        if (lastToken.type == TokenType::Operator) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+Token ExpressionParser::parseOperator(const std::string &expression, std::size_t &index,
+                                      const std::vector<Token> &output) const {
+    char ch = expression[index];
+    std::string op(1, ch);
+
+    if (ch == '+' || ch == '-') {
+        if (isUnaryOperator(expression, index, output)) {
+            ++index;
+            return Token{TokenType::Operator, ch == '-' ? "neg" : "+", 0.0};
+        }
+    }
+
+    if (operators_.find(op) == operators_.end()) {
+        throw InvalidInputException(std::string("Unsupported operator: ") + ch);
+    }
+
+    ++index;
+    return Token{TokenType::Operator, op, 0.0};
+}
+
+} // namespace sci_calc
+
+
diff --git a/src/ExpressionParser.h b/src/ExpressionParser.h
new file mode 100644
index 0000000..bf253ca
--- /dev/null
+++ b/src/ExpressionParser.h
@@ -0,0 +1,58 @@
+// ExpressionParser.h
+// Responsible for tokenizing and converting infix expressions to postfix notation
+
+#pragma once
+
+#include "Exceptions.h"
+
+#include <cstddef>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+namespace sci_calc {
+
+enum class TokenType {
+    Number,
+    Operator,
+    Function,
+    OpenParen,
+    CloseParen,
+    Constant
+};
+
+struct Token {
+    TokenType type;
+    std::string text;
+    double value = 0.0;
+};
+
+struct OperatorInfo {
+    int precedence;
+    bool rightAssociative;
+    int arity;
+};
+
+class ExpressionParser {
+public:
+    ExpressionParser();
+
+    std::vector<Token> parseToPostfix(const std::string &expression) const;
+
+private:
+    std::unordered_map<std::string, OperatorInfo> operators_;
+    std::unordered_map<std::string, double> constants_;
+
+    static bool isIdentifierChar(char ch);
+    Token parseNumber(const std::string &expression, std::size_t &index) const;
+    Token parseIdentifier(const std::string &expression, std::size_t &index) const;
+    Token parseOperator(const std::string &expression, std::size_t &index,
+                        const std::vector<Token> &output) const;
+
+    bool isUnaryOperator(const std::string &expression, std::size_t index,
+                         const std::vector<Token> &output) const;
+};
+
+} // namespace sci_calc
+
+
diff --git a/src/main.cpp b/src/main.cpp
new file mode 100644
index 0000000..67a9dcf
--- /dev/null
+++ b/src/main.cpp
@@ -0,0 +1,93 @@
+// main.cpp
+// Command-line interface for the Scientific Calculator
+
+#include "Calculator.h"
+
+#include <iostream>
+#include <string>
+#include <iomanip>
+
+void printUsage(const char *programName) {
+    std::cout << "Scientific Calculator\n";
+    std::cout << "Usage: " << programName << " [expression]\n\n";
+    std::cout << "If no expression is provided, the calculator runs in interactive mode.\n\n";
+    std::cout << "Supported operations:\n";
+    std::cout << "  Basic: +, -, *, /, %, ^ (power)\n";
+    std::cout << "  Functions: sin, cos, tan, asin, acos, atan\n";
+    std::cout << "             log (base 10), ln (natural), sqrt, exp, abs\n";
+    std::cout << "  Constants: pi, e\n";
+    std::cout << "\nExamples:\n";
+    std::cout << "  " << programName << " \"2 + 3 * 4\"\n";
+    std::cout << "  " << programName << " \"sin(pi/2)\"\n";
+    std::cout << "  " << programName << " \"sqrt(16) + log(100)\"\n";
+    std::cout << "  " << programName << " \"2^3 + 5\"\n";
+}
+
+int main(int argc, char *argv[]) {
+    sci_calc::Calculator calculator;
+
+    // If expression provided as command-line argument
+    if (argc > 1) {
+        std::string expression = argv[1];
+        if (expression == "-h" || expression == "--help") {
+            printUsage(argv[0]);
+            return 0;
+        }
+
+        try {
+            double result = calculator.calculate(expression);
+            std::cout << std::fixed << std::setprecision(10) << result << std::endl;
+            return 0;
+        } catch (const sci_calc::CalculatorException &e) {
+            std::cerr << "Error: " << e.what() << std::endl;
+            return 1;
+        } catch (const std::exception &e) {
+            std::cerr << "Unexpected error: " << e.what() << std::endl;
+            return 1;
+        }
+    }
+
+    // Interactive mode
+    std::cout << "Scientific Calculator - Interactive Mode\n";
+    std::cout << "Enter expressions to evaluate. Type 'quit' or 'exit' to exit.\n";
+    std::cout << "Type 'help' for usage information.\n\n";
+
+    std::string line;
+    while (true) {
+        std::cout << "> ";
+        if (!std::getline(std::cin, line)) {
+            break;
+        }
+
+        // Trim whitespace
+        line.erase(0, line.find_first_not_of(" \t\n\r"));
+        line.erase(line.find_last_not_of(" \t\n\r") + 1);
+
+        if (line.empty()) {
+            continue;
+        }
+
+        if (line == "quit" || line == "exit" || line == "q") {
+            std::cout << "Goodbye!\n";
+            break;
+        }
+
+        if (line == "help" || line == "h") {
+            printUsage(argv[0]);
+            continue;
+        }
+
+        try {
+            double result = calculator.calculate(line);
+            std::cout << std::fixed << std::setprecision(10) << result << std::endl;
+        } catch (const sci_calc::CalculatorException &e) {
+            std::cerr << "Error: " << e.what() << std::endl;
+        } catch (const std::exception &e) {
+            std::cerr << "Unexpected error: " << e.what() << std::endl;
+        }
+    }
+
+    return 0;
+}
+
+