diff --git a/calculator.cpp b/calculator.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..24eebe31f3576c5446d3932f11675349d2b26774
--- /dev/null
+++ b/calculator.cpp
@@ -0,0 +1,684 @@
+#include "calculator.h"
+#include <QPushButton>
+#include <QLCDNumber>
+#include <QGridLayout>
+#include <QDebug>
+#include <QObject>
+#include <QRadioButton>
+#include <QHBoxLayout>
+#include <QtMath>
+
+
+Calculator::Calculator(QWidget *parent)
+    : QWidget(parent),
+    f_lcdNum(0),
+    f_currentNum(""),
+    f_if_currNumChangable(true)
+{
+    setMinimumSize(600, 500);
+    this->setWindowTitle("Calculator (standard mode)");
+    MainLayout = new QGridLayout(this);
+    f_BtnLayoutCasual = new QGridLayout(this);  
+    f_BtnLayoutSciExtr = new QGridLayout(this); 
+    f_BtnLayoutSciExtrWidget = new QWidget(this);  
+    f_BtnLayoutCasualExtrWidget = new QWidget(this);   
+    f_HBoxBtnLayout = new QHBoxLayout(this);   
+
+    f_lcdNum = new QLCDNumber(12, this);
+    f_lcdNum->setSegmentStyle(QLCDNumber::Flat);
+    f_lcdNum->setMinimumSize(400,60);
+    f_lcdNum->setDigitCount(20);
+
+
+
+    f_radioBtnCasual = new QRadioButton("Casual", this);
+    f_radioBtnCasual->toggle();
+    f_radioBtnSci = new QRadioButton("Science", this);
+
+    connect(f_radioBtnCasual, SIGNAL(toggled(bool)), this, SLOT(slotHideSci(bool)));
+    connect(f_radioBtnSci, SIGNAL(toggled(bool)), this, SLOT(slotShowSci(bool)));
+    QString ButtonsTxtCasual[4][5] = {
+        {"7","8","9","/","sqrt"},
+        {"4","5","6","*","rev"},
+        {"1","2","3","-","sqr"},
+        {".","0","=","+","-x"}
+    };
+
+    QString ButtonsTxtSciExtr[4][4] = {
+        {"sinh", "sin", "exp", "ln"},
+        {"cosh", "cos", "n!", "log"},
+        {"tanh", "tan", "cubic sqr", "ysqr"},
+        {"pi", "e", "cubic root", "ysqrt"}
+    };
+
+
+
+    for (int row = 0; row < 4; row++)
+    {
+        for (int col = 0; col < 5; col++)
+        {
+            f_BtnLayoutCasual->addWidget(createButton(ButtonsTxtCasual[row][col], 30, 40), row+2, col);
+        }
+    }
+
+    for (int row = 0; row < 4; row++)
+    {
+        for (int col = 0; col < 4; col++)
+        {
+            f_BtnLayoutSciExtr->addWidget(createButton(ButtonsTxtSciExtr[row][col], 30, 40), row+2, col);
+        }
+    }
+
+    f_BtnLayoutSciExtrWidget->setLayout(f_BtnLayoutSciExtr);
+    f_BtnLayoutCasualExtrWidget->setLayout(f_BtnLayoutCasual);
+    f_HBoxBtnLayout->addWidget(f_BtnLayoutSciExtrWidget);
+    f_HBoxBtnLayout->addWidget(f_BtnLayoutCasualExtrWidget);
+    MainLayout->addWidget(f_lcdNum, 0, 0, 1, 7, Qt::AlignmentFlag::AlignHCenter);
+    MainLayout->addWidget(createButton("CE", 40, 35), 0, 8, Qt::AlignmentFlag::AlignCenter);
+
+    MainLayout->addWidget(f_radioBtnCasual, 1, 0, 1, 2, Qt::AlignmentFlag::AlignCenter);
+    MainLayout->addWidget(f_radioBtnSci, 1, 2, 1, 2, Qt::AlignmentFlag::AlignCenter);
+
+    MainLayout->addLayout(f_HBoxBtnLayout, 2, 0, 4, 9, Qt::AlignmentFlag::AlignCenter);
+
+    f_BtnLayoutSciExtrWidget->hide();
+    this->setLayout(MainLayout);
+    resize (500, 400);
+}
+
+QPushButton* Calculator::createButton(const QString &p_str, size_t p_horz, size_t p_vert)
+{
+    QPushButton* new_PBtn = new QPushButton(p_str);
+    new_PBtn->setMinimumSize(p_horz, p_vert);
+    connect(new_PBtn, SIGNAL(clicked()), this, SLOT(slotButtonClicked()));
+    return new_PBtn;
+}
+
+Calculator::~Calculator()  
+{}
+
+void Calculator::calc()
+{
+    if (f_operStack.size() < 2)
+        return;
+
+    if (f_operStack.size() == 2)
+    {
+        QString operation = f_operStack.pop();
+        double operand = f_operStack.pop().toDouble();
+        qDebug() << operand << operation << " 0 if binary";
+
+        if (operation == "rev")
+        {
+            if (operand == 0)
+            {
+                f_lcdNum->display("ERR");
+                qDebug() << "ERR";
+            }
+            else
+                f_lcdNum->display(1 / operand);
+            qDebug() << 1/operand;
+        }
+
+        if (operation == "sqr")
+        {f_lcdNum->display(operand * operand);
+        qDebug() << operand * operand;}
+
+        if (operation == "sqrt")
+        {f_lcdNum->display(sqrt(operand));
+        qDebug() << sqrt(operand);}
+
+        if(operation == "-x")
+        {f_lcdNum->display(-operand);
+        qDebug() << -operand;}
+
+        if(operation == "cubic root")
+        {   double tt = 1/3.0;
+            f_lcdNum->display(qPow(operand, tt));
+        qDebug() << qPow(operand, tt);}
+
+        if(operation == "cubic sqr")
+        {f_lcdNum->display(operand * operand * operand);
+        qDebug() << operand * operand * operand;}
+
+        if(operation == "n!")
+        {
+            int res = 1;
+            int oper = static_cast<int>(operand);
+            if (oper < 1)
+            {
+                f_lcdNum->display("Err");
+                return;
+            }
+            else
+            {
+                while (oper > 1)
+                {
+                    res *= oper;
+                    oper--;
+                }
+            }
+            f_lcdNum->display(res);
+        qDebug() << res;}
+
+        if (operation == "+" || operation == "-")
+        {f_lcdNum->display(operand);
+        qDebug() << operand;}
+
+        if (operation == "*")
+        {f_lcdNum->display(0);
+        qDebug() << 0;}
+
+        if (operation == "/")
+        {f_lcdNum->display("Err");
+        qDebug() << "Err";}
+
+        if (operation == "log")
+        {f_lcdNum->display("Err");
+        qDebug() << "Err";}
+
+        if(operation == "sin")
+        {f_lcdNum->display(qSin(operand));
+        qDebug() << qSin(operand);}
+
+        if(operation == "sinh")
+        {f_lcdNum->display(qAsin(operand));
+        qDebug() << qAsin(operand);}
+
+        if(operation == "cos")
+        {f_lcdNum->display(qCos(operand));
+        qDebug() << qCos(operand);}
+
+        if(operation == "cosh")
+        {f_lcdNum->display(qAcos(operand));
+        qDebug() << qAcos(operand);}
+
+        if(operation == "tan")
+        {f_lcdNum->display(qTan(operand));
+        qDebug() << qTan(operand);}
+
+        if(operation == "tanh")
+        {f_lcdNum->display(qAtan(operand));
+        qDebug() << qAtan(operand);}
+
+        if(operation == "ln")
+        {f_lcdNum->display(qLn(operand));
+        qDebug() << qLn(operand);}
+
+        if(operation == "exp")
+        {f_lcdNum->display(qExp(operand));
+        qDebug() << qExp(operand);}
+        if (operation == "ysqr")
+        {f_lcdNum->display(1);
+        qDebug() << 1;}
+
+        if (operation == "ysqrt")
+        {f_lcdNum->display("Err");
+        qDebug() << "Err";}
+
+
+    }
+    else if(f_operStack.size() == 3)
+    {
+
+        double operand2 = f_operStack.pop().toDouble();
+        QString operation = f_operStack.pop();
+        double operand1 = f_operStack.pop().toDouble();
+
+        qDebug() << operand1 << operation << operand2 << ":";
+
+        if (operation == "+")
+        {f_lcdNum->display(operand1 + operand2);
+        qDebug() << operand1 + operand2;}
+
+        if (operation == "-")
+        {f_lcdNum->display(operand1 - operand2);
+        qDebug() << operand1 - operand2;}
+
+        if (operation == "*")
+        {f_lcdNum->display(operand1 * operand2);
+        qDebug() << operand1 * operand2;}
+
+        if (operation == "/")
+        {f_lcdNum->display(operand1 / operand2);
+        qDebug() << operand1 / operand2;}
+
+        if (operation == "log")
+        {f_lcdNum->display(qLn(operand1) / qLn(operand2));
+        qDebug() << qLn(operand1) / qLn(operand2);}
+
+        if (operation == "ysqr")
+        {f_lcdNum->display(qPow(operand1, operand2));
+        qDebug() << qPow(operand1, operand2);}
+
+        if (operation == "ysqrt")
+        {f_lcdNum->display(qPow(operand1, 1.0 / operand2));
+        qDebug() << qPow(operand1, 1.0 / operand2);}
+    }
+    else if (f_operStack.size() == 5)
+    {   double operand3 = f_operStack.pop().toDouble();
+        QString operation2 = f_operStack.pop();
+        double operand2 = f_operStack.pop().toDouble();
+        QString operation1 = f_operStack.pop();
+        double operand1 = f_operStack.pop().toDouble();
+        double mid_res;
+
+        qDebug() << operand1 << operation1 << operand2 << operation2 << operand3 << ":";
+        if (operation2 == "*")
+        {mid_res = operand2 * operand3;
+        qDebug() << "mid_res = " << operand2 * operand3;}
+
+        if (operation1 == "+")
+        {f_lcdNum->display(operand1 + mid_res);
+        qDebug() << operand1 + mid_res;}
+
+        if (operation1 == "-")
+        {f_lcdNum->display(operand1 - mid_res);
+        qDebug() << operand1 - mid_res;}
+
+        if (operation1 == "*")
+        {f_lcdNum->display(operand1 * mid_res);
+        qDebug() << operand1 * mid_res;}
+
+        if (operation1 == "/")
+        {f_lcdNum->display(operand1 / mid_res);
+        qDebug() << operand1 / mid_res;}
+
+        if (operation1 == "log")
+        {f_lcdNum->display(qLn(operand1) / qLn(mid_res));
+        qDebug() << qLn(operand1) / qLn(mid_res);}
+
+        if (operation1 == "ysqr")
+        {f_lcdNum->display(qPow(operand1, mid_res));
+        qDebug() << qPow(operand1, mid_res);}
+
+        if (operation1 == "ysqrt")
+        {f_lcdNum->display(qPow(operand1, 1.0 / mid_res));
+        qDebug() << qPow(operand1, 1.0 / mid_res);}
+
+        if (operation2 == "/")
+        {mid_res = operand2 / operand3;
+        qDebug() << "mid_res = " << operand2 / operand3;}
+
+        if (operation2 == "log")
+        {mid_res = qLn(operand2) / qLn(operand3);
+        qDebug() << "mid_res = " << qLn(operand2) / qLn(operand3);}
+
+        if (operation2 == "ysqr")
+        {mid_res = qPow(operand2, operand3);
+        qDebug() << "mid_res = " << qPow(operand2, operand3);}
+
+        if (operation2 == "ysqrt")
+        {mid_res = qPow(operand2, 1.0 / operand3);
+        qDebug() << "mid_res = " << qPow(operand2, 1.0 / operand3);}
+    }
+}
+
+void Calculator::slotHideSci(bool p_is)
+{
+    if (p_is)
+    {
+        this->setWindowTitle("Casual (standard mode)");
+        f_BtnLayoutSciExtrWidget->hide();
+
+        setMinimumSize(600, 500);
+        resize(600,500);
+        qDebug() << "Resize (600, 500)";
+        f_lcdNum->setMinimumSize(400,60);
+        f_lcdNum->setDigitCount(20);
+    }
+}
+
+void Calculator::slotShowSci(bool p_is)
+{
+    if (p_is)
+    {
+        this->setWindowTitle("Upgrade Calculator (scientific mode)");
+        f_BtnLayoutSciExtrWidget->show();
+
+        setMinimumSize(900, 500);
+        resize(900, 500);
+
+        qDebug() << "Resize (900, 500)";
+        f_lcdNum->setMinimumSize(650,60);
+        f_lcdNum->setDigitCount(35);
+    }
+}
+
+
+void Calculator::slotButtonClicked()
+{
+    QPushButton* s = dynamic_cast<QPushButton*>(sender());
+    QString input;
+    if(s)
+        input = s->text();
+    else
+        return;
+
+    qDebug() << "Just pressed: " << input;
+
+    if (input == "CE")
+    {
+        f_operStack.clear();
+        f_currentNum = "";
+        f_lcdNum->display(0);
+        return;
+    }
+
+    if (input == "C")  
+    {
+        if (f_currentNum != "") 
+        {
+            f_currentNum = "";
+            f_lcdNum->display(0);
+            return;
+        }
+        else    //if not, clear stack
+        {
+            f_operStack.clear();
+            f_lcdNum->display(0);
+            return;
+        }
+    }
+
+    if (input.contains(QRegExp("[0-9]")))  
+    {
+        if (f_if_currNumChangable)  
+        {
+            if (input == "0" && f_currentNum == "") 
+            {
+                f_lcdNum->display(0);
+                return;
+            }
+            f_currentNum += input;  
+            f_lcdNum->display(f_currentNum);
+            return;
+        }
+        else    
+        {
+            f_if_currNumChangable = true;  
+            if (input == "0")   
+            {
+                f_currentNum = "";  
+                f_lcdNum->display(0);   
+                return;
+            }
+            f_currentNum = input;   
+            f_lcdNum->display(f_currentNum);
+            return;
+        }
+    }
+    else if (input == ".")           
+    {
+        if (f_currentNum == "")            
+        {
+            f_currentNum += "0.";   
+            f_lcdNum->display(f_currentNum);
+            return;
+        }
+        else   
+        {
+            if (f_if_currNumChangable)  
+            {
+                if (f_currentNum.contains('.')) 
+                {
+                    /*f_currentNum = "0.";
+                    f_lcdNum->display(f_currentNum);
+                    return;*/
+                    return;
+                }
+                f_currentNum += input;         
+                f_lcdNum->display(f_currentNum);
+                return;
+            }
+            else    //if not changable
+            {
+                f_if_currNumChangable = true;   
+                f_currentNum = "0.";    
+                f_lcdNum->display(f_currentNum);
+                return;
+            }
+         }
+    }
+    else if (NumND.contains(input)) 
+    {
+        if (input == "e")
+        {
+            f_currentNum = QString::number(qExp(1));
+            f_if_currNumChangable = false;     
+            f_lcdNum->display(f_currentNum);
+            return;
+        }
+        else
+        {
+            f_currentNum = QString::number(PI);
+            f_if_currNumChangable = false;     
+            f_lcdNum->display(f_currentNum);
+            return;
+        }
+    }
+    else        //if input is an operation
+    {
+        if (input == "=")   //if =
+        {
+            if (f_operStack.size() == 0)    
+            {
+                return;
+            }
+            else if (f_operStack.size() == 2)   
+            {
+                if (f_currentNum == "") 
+                {
+                    calc();
+                    return;
+                }
+                else   
+                {
+                    f_operStack.push_back(f_currentNum);   
+                    calc();
+                    f_operStack.clear();
+                    f_currentNum = "";
+                    return;
+                }
+            }
+            else   
+            {
+                if (f_currentNum == "") 
+                {
+                    f_operStack.pop_back(); 
+                    calc();
+                    f_operStack.clear();
+                    return;
+                }
+                else    
+                {
+                    f_operStack.push_back(f_currentNum);   
+                    f_currentNum = "";
+                    calc();
+                    f_operStack.clear();
+                    return;
+                }
+            }
+        }
+        else   
+        {
+            if (f_operStack.size() == 0)   
+            {
+                if (f_currentNum == "") 
+                {
+                    f_operStack.push_back(QString::number(f_lcdNum->value()));  
+                    f_operStack.push_back(input);   
+                    if (UnOp.contains(input))   
+                    {
+                        calc();
+                        f_operStack.clear();
+                        return;
+                    }
+                    return;
+                }
+                else    
+                {
+                    f_operStack.push_back(f_currentNum);
+                    f_currentNum = "";      
+                    f_operStack.push_back(input);
+                    if (UnOp.contains(input))
+                    {
+                        calc();
+                        f_operStack.clear();
+                        return;
+                    }
+                    return;
+                }
+            }
+            else if (f_operStack.size() == 2) 
+            {
+                if (f_currentNum == "")
+                {
+                    f_operStack.pop_back(); 
+                    f_operStack.push_back(input);
+                    if (UnOp.contains(input))
+                    {
+                        calc();
+                        f_operStack.clear();
+                        return;
+                    }
+                    return;
+                }
+                else   
+                {
+
+                    QString tech_oper;     
+                    tech_oper = f_operStack.pop();
+
+                    if (OpToCountimmediately.contains(tech_oper) || SumOp.contains(input))  
+                    {
+                        f_operStack.push_back(tech_oper);
+                        f_operStack.push_back(f_currentNum);    
+                        f_currentNum = "";
+                        calc();
+                        f_operStack.clear();
+                        f_operStack.push_back(QString::number(f_lcdNum->value())); 
+                        f_operStack.push_back(input);   
+                        return;
+                    }
+                    else
+                    {
+                        if (UnOp.contains(input))   
+                        {
+                            QString tech_f_operand; 
+                            tech_f_operand = f_operStack.pop();
+
+                            f_operStack.push_back(f_currentNum);   
+                            f_operStack.push_back(input);
+                            calc();
+                            f_operStack.clear();
+                            f_operStack.push_back(tech_f_operand);  
+                            f_operStack.push_back(tech_oper);
+                            f_currentNum = QString::number(f_lcdNum->value());  
+                            f_if_currNumChangable = false; 
+                            return;
+                        }
+                        else    //else add second number and second operation to stack
+                        {
+                            f_operStack.push_back(f_currentNum);
+                            f_currentNum = "";
+                            f_operStack.push_back(input);
+                            return;
+                        }
+                    }
+                }
+            }
+            else    
+            {
+                if (f_currentNum == "") 
+                {
+                    f_operStack.pop_back(); //drop operation 2
+                    if (UnOp.contains(input))   
+                    {
+                        QString tech_f_operand;
+                        QString tech_s_operand;
+                        QString tech_oper;
+                        tech_s_operand = f_operStack.pop();
+                        tech_oper = f_operStack.pop();
+                        tech_f_operand = f_operStack.pop();
+                        f_operStack.push_back(tech_s_operand);
+                        f_operStack.push_back(input);
+                        calc();
+                        f_operStack.clear();
+                        f_operStack.push_back(tech_f_operand);
+                        f_operStack.push_back(tech_oper);
+                        f_currentNum = QString::number(f_lcdNum->value());
+                        return;
+                    }
+                    else    
+                    {
+                        f_operStack.push_back(input);
+                        return;
+                    }
+                }
+                else    
+                {
+                    if (UnOp.contains(input))   
+                    {
+                        QString tech_f_operand;
+                        QString tech_s_operand;
+                        QString tech_oper1;
+                        QString tech_oper2;
+
+                        tech_oper2 = f_operStack.pop();
+                        tech_s_operand = f_operStack.pop();     
+                        tech_oper1 = f_operStack.pop();
+                        tech_f_operand = f_operStack.pop();
+
+                        f_operStack.push_back(f_currentNum);    
+                        f_operStack.push_back(input);
+                        calc();
+                        f_operStack.clear();
+                        f_currentNum = QString::number(f_lcdNum->value());  
+                        f_if_currNumChangable = false;  
+
+                        f_operStack.push_back(tech_f_operand);
+                        f_operStack.push_back(tech_oper1);  
+                        f_operStack.push_back(tech_s_operand);
+                        f_operStack.push_back(tech_oper2);
+                        return;
+                    }
+                    else    //if inputed operation 3 is binary
+                    {
+                        if (SumOp.contains(input))  
+                        {
+                            f_operStack.push_back(f_currentNum);   
+                            f_currentNum = "";
+                            calc();
+                            f_operStack.clear();
+                            f_operStack.push_back(QString::number(f_lcdNum->value())); 
+                            f_operStack.push_back(input);   
+                            return;
+                        }
+                        QString tech_f_operand;
+                        QString tech_s_operand;
+                        QString tech_oper1;
+                        QString tech_oper2;
+
+                        tech_oper2 = f_operStack.pop();
+                        tech_s_operand = f_operStack.pop();
+                        tech_oper1 = f_operStack.pop();
+                        tech_f_operand = f_operStack.pop();
+
+                        f_operStack.push_back(tech_s_operand); 
+                        f_operStack.push_back(tech_oper2);
+                        f_operStack.push_back(f_currentNum);
+                        calc();
+                        f_operStack.clear();
+                        f_operStack.push_back(tech_f_operand); 
+                        f_operStack.push_back(tech_oper1);
+                        f_operStack.push_back(QString::number(f_lcdNum->value()));
+                        f_operStack.push_back(input);
+                        f_currentNum = "";
+                        return;
+                    }
+                }
+            }
+        }
+    }
+}