Program to read a Non-Linear equation in one variable, then evaluate it using Simple Itrative Method and display its kD accurate root

 # include <iostream.h>
 # include <string.h>
 # include <stdlib.h>
 # include <conio.h>
 # include <math.h>

 const int max_size=30;

 int top=-1;
 int iterations=0;

 long double x0=0;
 long double xn=0;

 char Non_linear_equation[100]={NULL};
 char Stack[max_size][max_size]={NULL};
 char Postfix_expression[max_size][max_size]={NULL};



 //-----------------------  Function Prototypes  -------------------------//



 void push(const char *);
 void convert_infix_expression_to_postfix_expression(const char *);

 const char* pop( );
 const long double evaluate_postfix_expression(const long double);

 void show_screen( );
 void clear_screen( );
 void get_input_non_linear_equation( );
 void apply_simple_itrative_method( );
 void show_result( );



 //------------------------------  main( )  ------------------------------//



 int main( )
    {
       clrscr( );
       textmode(C4350);

       show_screen( );
       get_input_non_linear_equation( );
       apply_simple_itrative_method( );
       show_result( );

       getch( );
       return 0;
    }



 //----------------------  Function Definitions  -------------------------//




 //--------------------------  push(const char*)  ------------------------//


 void push(const char* Operand)
    {
       if(top==(max_size-1))
      {
         cout<<\"Error : Stack is full.\"<<endl;
         cout<<\"\\n        Press any key to exit.\";

         getch( );
         exit(0);
      }

       else
      {
         top++;
         strcpy(Stack[top],Operand);
      }
    }


 //------------------------------  pop( )  -------------------------------//


 const char* pop( )
    {
       char Operand[40]={NULL};

       if(top==-1)
      {
         cout<<\"Error : Stack is empty.\"<<endl;
         cout<<\"\\n        Press any key to exit.\";

         getch( );
         exit(0);
      }

       else
      {
         strcpy(Operand,Stack[top]);
         strset(Stack[top],NULL);
         top--;
      }

       return Operand;
    }


 //----  convert_infix_expression_to_postfix_expression(const char*)  ----//


 void convert_infix_expression_to_postfix_expression(const char* Expression)
    {
       char Infix_expression[100]={NULL};
       char Symbol_scanned[30]={NULL};

       push(\"(\");
       strcpy(Infix_expression,Expression);
       strcat(Infix_expression,\"+0)\");

       int flag=0;
       int count_1=0;
       int count_2=0;
       int equation_length=strlen(Infix_expression);

       if(Infix_expression[0]==\'(\')
      flag=1;

       do
      {
         strset(Symbol_scanned,NULL);

         if(flag==0)
        {
           int count_3=0;

           do
              {
             Symbol_scanned[count_3]=Infix_expression[count_1];

             count_1++;
             count_3++;
              }
           while(count_1<=equation_length &&
               Infix_expression[count_1]!=\'(\' &&
                  Infix_expression[count_1]!=\'+\' &&
                 Infix_expression[count_1]!=\'-\' &&
                    Infix_expression[count_1]!=\'*\' &&
                       Infix_expression[count_1]!=\'/\' &&
                      Infix_expression[count_1]!=\'^\' &&
                         Infix_expression[count_1]!=\')\');


           flag=1;
        }

         else if(flag==1)
        {
           Symbol_scanned[0]=Infix_expression[count_1];

           count_1++;

           if(Infix_expression[count_1]!=\'(\' &&
             Infix_expression[count_1]!=\'^\' &&
                Infix_expression[count_1]!=\'*\' &&
                   Infix_expression[count_1]!=\'/\' &&
                  Infix_expression[count_1]!=\'+\' &&
                     Infix_expression[count_1]!=\'-\' &&
                    Infix_expression[count_1]!=\')\')
              flag=0;

           if(Infix_expression[count_1-1]==\'(\' &&
               (Infix_expression[count_1]==\'-\' ||
                 Infix_expression[count_1]==\'+\'))
              flag=0;
        }

         if(strcmp(Symbol_scanned,\"(\")==0)
        push(\"(\");

         else if(strcmp(Symbol_scanned,\")\")==0)
        {
           while(strcmp(Stack[top],\"(\")!=0)
              {
             strcpy(Postfix_expression[count_2],pop( ));

             count_2++;
              }

           pop( );
        }

         else if(strcmp(Symbol_scanned,\"^\")==0 ||
               strcmp(Symbol_scanned,\"+\")==0 ||
                 strcmp(Symbol_scanned,\"-\")==0 ||
                       strcmp(Symbol_scanned,\"*\")==0 ||
                         strcmp(Symbol_scanned,\"/\")==0)
        {
           if(strcmp(Symbol_scanned,\"^\")==0)
              {  }

           else if(strcmp(Symbol_scanned,\"*\")==0 ||
                          strcmp(Symbol_scanned,\"/\")==0)
              {
             while(strcmp(Stack[top],\"^\")==0 ||
                     strcmp(Stack[top],\"*\")==0 ||
                       strcmp(Stack[top],\"/\")==0)
                {
                   strcpy(Postfix_expression[count_2],pop( ));

                   count_2++;
                }
              }

           else if(strcmp(Symbol_scanned,\"+\")==0 ||
                    strcmp(Symbol_scanned,\"-\")==0)
              {
             while(strcmp(Stack[top],\"(\")!=0)
                {
                   strcpy(Postfix_expression[count_2],pop( ));

                   count_2++;
                }
              }

           push(Symbol_scanned);
        }

         else
        {
           strcat(Postfix_expression[count_2],Symbol_scanned);

           count_2++;
        }
      }
       while(strcmp(Stack[top],NULL)!=0);

       strcat(Postfix_expression[count_2],\"=\");
       count_2++;
    }


 //----------  evaluate_postfix_expression(const long double)  -----------//


 const long double evaluate_postfix_expression(const long double x)
    {
       long double function_value=0;

       int count_1=-1;

       char Symbol_scanned[30]={NULL};

       do
      {
         count_1++;

         strcpy(Symbol_scanned,Postfix_expression[count_1]);

         if(strcmp(Symbol_scanned,\"^\")==0 ||
              strcmp(Symbol_scanned,\"*\")==0 ||
                strcmp(Symbol_scanned,\"/\")==0 ||
                  strcmp(Symbol_scanned,\"+\")==0 ||
                    strcmp(Symbol_scanned,\"-\")==0)

        {
           char Result[30]={NULL};
           char Operand[2][30]={NULL};

           strcpy(Operand[0],pop( ));
           strcpy(Operand[1],pop( ));

           long double operand[2]={0};
           long double result=0;

           char *endptr;

           for(int count_2=0;count_2<2;count_2++)
              {
             int flag=0;

             if(Operand[count_2][0]==\'-\')
                {
                   int length=strlen(Operand[count_2]);

                   for(int count_3=0;count_3<(length-1);count_3++)
                  Operand[count_2][count_3]=Operand[count_2][(count_3+1)];

                   Operand[count_2][count_3]=NULL;

                   flag=1;
                }

             if(strcmp(Operand[count_2],\"x\")==0)
                operand[count_2]=x;

             else if(strcmp(Operand[count_2],\"e\")==0)
                operand[count_2]=2.718282;

             else if(strcmp(Operand[count_2],\"sinx\")==0)
                operand[count_2]=sinl(x);

             else if(strcmp(Operand[count_2],\"cosx\")==0)
                operand[count_2]=cosl(x);

             else if(strcmp(Operand[count_2],\"tanx\")==0)
                operand[count_2]=tanl(x);

             else if(strcmp(Operand[count_2],\"lnx\")==0)
                operand[count_2]=logl(x);

             else if(strcmp(Operand[count_2],\"logx\")==0)
                operand[count_2]=log10l(x);

             else
                operand[count_2]=strtod(Operand[count_2],&endptr);

             if(flag)
                operand[count_2]*=-1;
              }

           switch(Symbol_scanned[0])
              {
             case \'^\' : result=powl(operand[1],operand[0]);
                    break;

             case \'*\' : result=operand[1]*operand[0];
                    break;

             case \'/\' : result=operand[1]/operand[0];
                    break;

             case \'+\' : result=operand[1]+operand[0];
                    break;

             case \'-\' : result=operand[1]-operand[0];
                    break;
              }

           gcvt(result,25,Result);

           push(Result);
        }

         else if(strcmp(Symbol_scanned,\"=\")!=0)
        push(Symbol_scanned);
      }
       while(strcmp(Symbol_scanned,\"=\")!=0);

       char Function_value[30]={NULL};
       char *endptr;

       strcpy(Function_value,pop( ));
       function_value=strtod(Function_value,&endptr);

       return function_value;
    }


 //--------------------------  show_screen( )  ---------------------------//


 void show_screen( )
    {
       cprintf(\"\\n********************************************************************************\");
       cprintf(\"*************************-                          -***************************\");
       cprintf(\"*------------------------- \");

       textbackground(1);
       cprintf(\" Simple Itrative Method \");
       textbackground(8);

       cprintf(\" ---------------------------*\");
       cprintf(\"*************************-                          -***************************\");
       cprintf(\"********************************************************************************\");

       for(int count=0;count<42;count++)
      cprintf(\"*                                                                              *\");

       gotoxy(1,46);
       cprintf(\"********************************************************************************\");
       cprintf(\"*------------------------------------------------------------------------------*\");
       cprintf(\"********************************************************************************\");

       gotoxy(1,2);
    }


 //-------------------------  clear_screen( )  ---------------------------//


 void clear_screen( )
    {
       for(int count=0;count<37;count++)
      {
         gotoxy(3,8+count);
         cout<<\"                                                                            \";
      }

       gotoxy(1,2);
    }


 //------------------- get_input_non_linear_equation( )  -----------------//


 void get_input_non_linear_equation( )
    {
       gotoxy(4,11);
       cout<<\"Non-Linear Equation with One Variable:\";

       gotoxy(4,12);
       cout<<\"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ\";

       gotoxy(6,37);
       cout<<\"Note : Write the function with proper Braces ( ) e.g; 2x+3 as (2*x)+3\";

       gotoxy(6,40);
       cout<<\"Available Operators  :  ^ (raised to power) , * , / , + , -\";

       gotoxy(6,42);
       cout<<\"Available Operands   :  x , e , sinx , cosx , tanx , lnx , logx ,\";

       gotoxy(6,44);
       cout<<\"                        n = any number\";

       gotoxy(4,14);
       cout<<\"Enter the Function with variabel x = f(x) = \";
       cin>>Non_linear_equation;

       gotoxy(4,17);
       cout<<\"Enter the Starting value = x0 =  \";
       cin>>x0;

       gotoxy(4,20);
       cout<<\"Enter the number of iterations  =  \";
       cin>>iterations;

       gotoxy(1,2);
    }


 //------------------  apply_simple_itrative_method( )  ------------------//


 void apply_simple_itrative_method( )
    {
       clear_screen( );

       gotoxy(4,10);
       cout<<\"Solution :\";

       gotoxy(4,11);
       cout<<\"ÍÍÍÍÍÍÍÍÍÍ\";

       convert_infix_expression_to_postfix_expression(Non_linear_equation);

       gotoxy(4,13);
       cout<<\"ÚÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿\";

       gotoxy(4,14);
       cout<<\"³    n    ³         Xn          ³\";

       gotoxy(4,15);
       cout<<\"ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ\";

       gotoxy(4,16);
       cout<<\"³         ³                     ³\";

       xn=x0;

       long double fx=0;

       int x_cord=4;
       int y_cord=17;

       for(int count_1=1;count_1<=iterations;count_1++)
      {
         gotoxy(x_cord,y_cord);
         cout<<\"³         ³                     ³\";

         gotoxy(x_cord,(y_cord+1));
         cout<<\"³         ³                     ³\";

         gotoxy((x_cord+4),y_cord);
         cout<<count_1;

         fx=evaluate_postfix_expression(xn);
         xn=fx;

         gotoxy((x_cord+13),y_cord);
         cout<<fx;

         y_cord+=2;

         if((count_1%12)==0 && count_1<iterations)
        {
           y_cord=17;

           gotoxy(30,44);
           cout<<\"Press any key to continue...\";
           getch( );

           for(int count_2=1;count_2<25;count_2++)
              {
             gotoxy(3,(16+count_2));
             cout<<\"                                                                            \";
              }
        }
      }

       gotoxy(x_cord,y_cord);
       cout<<\"ÀÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ\";

       gotoxy(30,44);
       cout<<\"Press any key to continue...\";
       getch( );
    }


 //---------------------------  show_result( )  --------------------------//


 void show_result( )
    {
       clear_screen( );

       gotoxy(6,10);
       cout<<\"Function of Non-Linear Equation :\";

       gotoxy(6,11);
       cout<<\"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ\";

       gotoxy(10,13);
       cout<<\"f(x)  =  \"<<Non_linear_equation;

       gotoxy(6,17);
       cout<<\"Starting Value = x0 = \"<<x0;

       gotoxy(6,19);
       cout<<\"Number of Iterations =  \"<<iterations;

       gotoxy(6,25);
       cout<<\"Required Root :\";

       gotoxy(6,26);
       cout<<\"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍ\";

       gotoxy(10,28);
       cout<<\"x  =  \"<<xn;

       gotoxy(1,2);
    }