/*Dwayne Cambridge */
/*Fermi National Accelerator Laboratory*/
/*Completed July 31, 2001*/

/* This program will act as a simple calculator. It will add, subtract, divide and multipy integer numbers only*/

#include <stdio.h>

/* Used to write to the serial port for the LCD */
#include <stdlib.h>
#include <unistd.h>
#include <termios.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>

        
float   Result,         /*Used to compute and store final result*/
        NewOperands[50]; /*Array used to store results of *,/ when operator precedence is needed*/
        
int     quit;           /*Used to keep program running in an infinite loop*/

int     flag,           /*Flag used to indicate when operator precedence is needed*/
        flag1,          /*Flag used to indicate when * or / is seperated by + or -*/
        Counter;        /*Used as a counter for the NewOperands Array*/

struct termios portset;
int contrast = 140;
char device[256] = "/dev/lcd";
int speed = B19200;
int temp;
static int fd;
char out[80];
char in[1],zero[1],nothing[1];
char zero_1[1];
ssize_t temp2;

int     number,         /*Used to store numbers into Operands array*/
        i,              /*Used as an index*/
        clear;          /*Used as a flag to indicate user wants to 
clear LCD screen*/
int     ind,            /*Used as an index*/
        indnum,         /*Used as an index*/
        indchar,        /*Used as an index*/
        start;          /*Used to indicate when the first kew was pressed on the LCD*/
char    Oper;           /*Used indicate which operator was pressed*/
char    TempOperands[10], /*Array used to store Operands as strings*/
        *p_array;       /*Used to convert strings to int */
float   Operands[50],   /*Used to store operands*/
        TempOperands1[50]; /*Used to read in operands*/
char    Operators[50],  /*Used to store Operators */
        TempOperators[50], /*Used to read in Operators */
        All[200];       /*Used to track every key press on LCD by user*/
        
int     Position,       /*Used as index*/
        row,            /*Tracks row to write to on LCD screen*/
        column,         /*Tracks column to write to on LCD screen*/
        digits,         /*Used to determine how many digits to write to LCD screen*/
        r,              /*Tracks row to write to on LCD screen*/
        c;              /*Tracks column to write to on LCD screen*/

void ReadWriteInt();
void ClearScreen();
void Write_To_LCD(float num);
void Initialize();
int InitializePort();
void InitializeLCD();
void OperandsOperators();

main()
{
        /*Function used to initialize flags and values used to compute the final result*/
        Initialize();
        
        /*Function used to initialize and open the port for writing*/
        temp = InitializePort();
        if(temp == -1)
        {
                printf("\nPort not open\n");
                quit = 0;
        }
        
        /*Function used to Initialize the LCD for writing*/
        InitializeLCD();

        while (quit == 1)
        {
                
          OperandsOperators();
          
          /* Computing the result */
        
          /*Do the following if only valid operators have been entered by the user*/  
          i = 0;
          flag1 = 0;
          if (quit == 1)
          {
                /*Loop through the Operators array until all valid Operators have been processed*/
                while(Operators[i] != '=')
                {
                        /*Check if Operator = /*/
                        if(Operators[i] == '/')
                        {
                                /*If Result is not equal to 1000000 then there has been a strind of *,/ */
                                /*Continue computing result using next operand (ex. 5+5*4/10)*/
                                /*This will detect if operator precedence is needed*/
                                if(Result != 1000000.0)
                                {
                                        Result = Result / Operands[i+1];
                                        /*Store result in NewOperands array, reset result, indicate*/
                                        /*operator precedence is needed*/
                                        if((Operators[i+1] == '+') || (Operators[i+1] == '-'))
                                        {
                                                NewOperands[Counter] = Result;
                                                Counter = Counter + 1;
                                                Result = 1000000.0;
                                                flag = 1;
                                        }
                                        /*If this is the last operator and no precedence is needed */
                                        /*then do not change value of result (ex. 1/1/1)*/ 
                                        if ((Operators[i+1] == '=') && (flag == 0))
                                        {
                                                Result = Result;
                                        }
                                        /*If this is the last operator and precedence is needed then store result*/
                                        else if(Operators[i+1] == '=')
                                        {
                                                NewOperands[Counter] = Result;
                                                Counter = Counter + 1;
                                                Result = 1000000.0;
                                        }
                                }
                                /*This is the begining of a new computation or this will compute values */
                                /*for operator precedence of an old computation */
                                /*(ex. will compute 5*4 first in (5+5*4/10) */
                                else
                                {
                                        Result = Operands[i] / Operands[i+1];
                                        /*If operator precedence exists*/
                                        if (flag1 == 1)
                                        {
                                                if((Operators[i+1] != '*') && (Operators[i+1] != '/'))
                                                {
                                                        NewOperands[Counter] = Result;
                                                        Counter = Counter + 1;
                                                        Result = 1000000.0;
                                                        flag1 = 0;
                                                }
                                        }
                                        /*Store result of computations for *,/ and indicate operator precedence*/
                                        else if((Operators[i+1] == '+') || (Operators[i+1] == '-'))
                                        {
                                                NewOperands[Counter] = Result;
                                                Counter = Counter + 1;
                                                Result = 1000000.0;
                                                flag = 1;
                                        }
                                        /*If this is the last operator and no precedence is needed */
                                        /*then do not change value of result (ex. 1/1/1)*/ 
                                        if ((Operators[i+1] == '=') && (flag == 0))
                                        {
                                                Result = Result;
                                        }
                                        /*If this is the last operator and precedence is needed then store result*/
                                        else if(Operators[i+1] == '=')
                                        {
                                                NewOperands[Counter] = Result;
                                                Counter = Counter + 1;
                                                Result = 1000000.0;
                                        }
                                }
                        }
                        /*Check if Operator = * */
                        /*The following code (logic) operates the same for multiply as it did for divide*/
                        else if(Operators[i] == '*')
                        {
                                /*Continue computing string of *,/ (ex 5*4/10 in 5+5*4/10) and indicate operator precedence*/
                                if(Result != 1000000.0)
                                {
                                        Result = Result * Operands[i+1];
                                        if((Operators[i+1] == '+') || (Operators[i+1] == '-'))
                                        {
                                                NewOperands[Counter] = Result;
                                                Counter = Counter + 1;
                                                Result = 1000000.0;
                                                flag = 1;
                                        }
                                        /*End of valid operators, no precedence is needed*/
                                        if ((Operators[i+1] == '=') && (flag == 0))
                                        {
                                                Result = Result;
                                        }
                                        /*End of string and precedence is needed - store result*/
                                        else if(Operators[i+1] == '=')
                                        {
                                                NewOperands[Counter] = Result;
                                                Counter = Counter + 1;
                                                Result = 1000000.0;
                                        }
                                }
                                /*Begining of computation or begining of string of *,/ */
                                else
                                {
                                        Result = Operands[i] * Operands[i+1];
                                        /*The computation has the following order: ex. 8*8+7*7+6*6 */
                                        if (flag1 == 1)
                                        {
                                                if((Operators[i+1] != '*') && (Operators[i+1] != '/'))
                                                {
                                                        NewOperands[Counter] = Result;
                                                        Counter = Counter + 1;
                                                        Result = 1000000.0;
                                                        flag1 = 0;
                                                }
                                        }
                                        /*The next Operator is + or - */
                                        else if((Operators[i+1] == '+') || (Operators[i+1] == '-'))
                                        {
                                                NewOperands[Counter] = Result;
                                                Counter = Counter + 1;
                                                Result = 1000000.0;
                                                flag = 1;
                                        }
                                        /*Reached the end of the computation and no precedence is necessary  */
                                        if ((Operators[i+1] == '=') && (flag == 0))
                                        {
                                                Result = Result;
                                        }
                                        /*Reached the end of the computation and precedence is necessary */
                                        else if(Operators[i+1] == '=')
                                        {
                                                NewOperands[Counter] = Result;
                                                Counter = Counter + 1;
                                                Result = 1000000.0;
                                        }
                                }
                        }
                        /* The current operator is not equal to * or / */
                        /* The following logic will create the NewOperands array as well as set flags */
                        else
                        {
                                if (i==0)
                                {
                                        if((Operators[i+1] == '*') || (Operators[i+1] == '/'))
                                                flag = 1;
                                        NewOperands[Counter] = Operands[i];
                                        Counter = Counter + 1;
                                        if((Operators[i+1] == '+') || (Operators[i+1] == '-'))
                                        {
                                                if((Operators[i+2] == '*') || (Operators[i+2] == '/'))
                                                {
                                                        NewOperands[Counter] = Operands[i+1];
                                                        Counter = Counter + 1;
                                                }
                                        }
                                }
                                else if((Operators[i-1] == '*') || (Operators[i-1] == '/'))
                                {
                                        if((Operators[i+1] == '*') || (Operators[i+1] == '/'))
                                        {
                                                Result = 1000000.0;
                                                flag1 = 1;
                                        }
                                        else if((Operators[i+1] == '-') || (Operators[i+1] =='+')|| (Operators[i+1] == '='))
                                        {
                                                NewOperands[Counter] = Operands[i+1];
                                                Counter = Counter + 1;
                                        }       
                                }
                                else if((Operators[i-1] == '+') || (Operators[i-1] == '-'))
                                { 
                                        if((Operators[i+1] == '+') || (Operators[i+1] == '-') || (Operators[i+1] == '='))
                                        {
                                                if (i == 1)
                                                {
                                                        NewOperands[Counter] = Operands[i];
                                                        Counter = Counter + 1;
                                                }
                                                else
                                                {
                                                        NewOperands[Counter] = Operands[i+1];
                                                        Counter = Counter + 1;
                                                }       
                                        }
                                        else if((Operators[i+1] == '*') ||(Operators[i+1] == '/'))
                                        {
                                                if (flag == 0)
                                                {
                                                        Result = 1000000.0;
                                                        flag = 1;
                                                        if(i != 1)
                                                        {
                                                                NewOperands[Counter] = Operands[i];
                                                                Counter = Counter + 1;
                                                        }
                                                }
                                                else
                                                {
                                                        Result = 1000000.0;
                                                        /*NewOperands[Counter] = Operands[i];
                                                        Counter = Counter + 1;*/
                                                        flag = 1;
                                                }
                                        }
                                }
                                else
                                {
                                        NewOperands[Counter] = Operands[i+1];
                                        Counter = Counter + 1;
                                }
                        }
                        i = i+1;
                }
                
                /*If there is precedence then reset the result and use the */
                /*NewOperands array to compute the result */
                if(flag == 1)
                        Result = 1000000.0;
                Counter = 0;
                
                /*Printing for testing purposes
                for(i=0; i<10; i = i+1)
                        printf("%f ", NewOperands[i]);
                printf("\n");
                for(i=0; i<20;i=i+1)
                        printf("%c ", All[i]);
                printf("\n");
                printf("the flag = %d\n", flag); */
                
                i = 0;
                
                /* Loop through Operator array */
                while(Operators[i] != '=')
                {
                        /*If precedence exists compute the result using the NewOperands array*/
                        if(flag == 1)
                        {
                                if (Operators[i] == '+')
                                {
                                        if(Result == 1000000.0)
                                        {
                                                Result = NewOperands[Counter] + NewOperands[Counter+1];
                                                Counter = 2;
                                        }
                                        else
                                        {
                                                Result = Result + NewOperands[Counter];
                                                Counter = Counter + 1;
                                        }
                                }
                                else if (Operators[i] == '-')
                                {
                                        if(Result == 1000000.0)
                                        {
                                                Result = NewOperands[Counter] - NewOperands[Counter+1];
                                                Counter = 2;
                                        }
                                        else
                                        {
                                                Result = Result - NewOperands[Counter];
                                                Counter = Counter + 1;
                                        }
                                }
                                
                        }
                        /*If precedence does not exist then the computation only */
                        /*is composed of + and -. Use the Operands array to compute the result*/
                        else
                        {
                                if (Operators[i] == '+')
                                {
                                        if(Result == 1000000.0)
                                        {
                                                Result = Operands[i] + Operands[i+1];
                                        }
                                        else
                                        {
                                                Result = Result + Operands[i+1];
                                        }
                                }
                                if (Operators[i] == '-')
                                {
                                        if(Result == 1000000.0)
                                        {
                                                Result = Operands[i] - Operands[i+1];
                                        }
                                        else
                                        {
                                                Result = Result - Operands[i+1];
                                        }
                                }
                        }
                        
                        i = i+1;
                }
          }
          
          /*Print the result to the screen*/
          /*Write the result to the LCD screen*/
          /*Indicate result written in All array*/
          if(quit == 1)
          {
                printf("> %f\n", Result);
                Write_To_LCD(Result);
                All[Position] = '$';
                Position = Position + 1;
                printf("> ");
          }
          
          /*Reset the calculator if port was not opened*/
          /*Set into an infinite loop*/
          if (quit == 0)
                quit = 1;
        }
        
        /*Close the Port */
        close (fd);
}

/*Used to initialize flags and values used to compute the result */
void Initialize()
{
        /*Go to Position: Column 1 Row 1 */
        sprintf (out, "%cG%c%c", 254, 1, 1);
        write(fd,out,4);
   
        /*Print the Result */
        sprintf (out, "%c", "Ready");
        write(fd,out,5);
        
        /*When quit = 0 Port was not opened*/
        quit = 1;
        
        
        number = -1;
        start = 1;
        clear = 0;
        Position = -1;
        row = 1;
        column = 1;
        digits = 0;
        r = 0;
        c = 0;
        
        /*Indicates a new computation*/
        Result = 1000000.0;
}

/*Used to open the port */
int InitializePort()
{
        /*Open and set port for writing*/
        fd = open (device, O_RDWR | O_NOCTTY);
   
        if (fd == -1) 
        {
           fprintf (stderr, "InitializePort: failed (%s)\n", strerror (errno));
           printf ("InitializePort: failed (%s)\n", strerror (errno));
           return -1;
        }
        tcgetattr (fd, &portset);
        cfsetospeed (&portset, speed);
        cfsetispeed (&portset, speed);
	cfmakeraw (&portset);
        tcsetattr (fd, TCSANOW, &portset);

}

/*Used to Initialize the LCD for writing */
void InitializeLCD()
{

        /*Go to Position: Column 1 Row 1 */
        sprintf (out, "%cG%c%c", 254, column, row);
        write(fd,out,4);
        
        /*Clear Key Buffer*/
        sprintf(out, "%cE", 254);
        write(fd,out,2);
        
        /*Turn AutoTransmit Keypresses Off*/
        sprintf (out,"%cO", 254);
        write(fd,out,2);
        sprintf (nothing,"%c",0);
        
        ClearScreen();
}

/* Used to read in Operators and Operands from the LCD and store them into appropriate arrays*/
void OperandsOperators()
{
        /*Clear and Initialize all arrays used to compute the result*/
        for(i=0; i<50; i++)
                Operands[i] = -1;
                        
        for(i=0; i<50; i++)
                NewOperands[i] = -1;
        
        for(i=0; i<50; i++)
                TempOperands1[i] = -1;
        
        for(i=0; i<50; i++)
                Operators[i] = '$';
                
        for(i=0; i<10; i++)
                TempOperands[i] = ' ';
                
        for(i=0; i<50; i++)
                TempOperators[i] = '$';
                        
        for(i=0; i<200; i++)
                All[i] = '$';
                        
                
        i = 0;
        flag = 0;
        Counter = 0;
        start = 1;
        
        /*Loop until the user enters an = on the LCD */ 
        while (TempOperators[indchar] != '=')
        {
                /* Call the function that interfaces with LCD */
                ReadWriteInt();
                /* If the clear button was pressed on the LCD, then clear and initialize all arrays*/
                if(clear == 1)
                {
                        ClearScreen();
                                
                        for(i=0; i<50; i++)
                                Operands[i] = -1;
                                        
                        for(i=0; i<50; i++)
                                NewOperands[i] = -1;
        
                        for(i=0; i<50; i++)
                                TempOperands1[i] = -1;
        
                        for(i=0; i<50; i++)
                                Operators[i] = '$';
                
                        for(i=0; i<10; i++)
                                TempOperands[i] = ' ';
                                        
                        for(i=0; i<50; i++)
                                TempOperators[i] = '$';
                        
                        for(i=0; i<200; i++)
                                All[i] = '$';   
                                
                        number = -1;
                        start = 1;
                                Result = 1000000.0;
                        }
                }
                
                
                /*Place operators in Operators array starting at position 0 if positioning is off*/
                /*if positioning is off then the user has computed a result and it continuing with the computation*/
                if(TempOperators[0] == '$')
                {
                        for(i=0;i<50;i++)
                                Operators[i] = TempOperators[i+1];
                }
                else
                {
                        for(i=0;i<50;i++)
                                Operators[i] = TempOperators[i];
                }
                
                /*Copy int values of operands into Operands array*/
                for(i=0;i<50;i++)
                        Operands[i] = TempOperands1[i];
                
                /*If we are not reading in a negative number */
                if(All[0] != '-')
                {
                        if(Operands[0] == 0)
                                Operands[0] = Result;
                }
                
                /*Printing for testing purposes
                for(i=0; i<ind; i = i+1)
                        printf("%d ", Operands[i]);
                printf("\n");
                for(i=0; i<indchar; i = i+1)
                        printf("%c ", Operators[i]);
                printf("\n");*/
}

/* Will read from the LCD store in the appropriate array and write the key press to the LCD screen */
void ReadWriteInt()
{        
         clear = 0;
         
         /*Poll Keypad*/
         sprintf (out,"%c&", 254);
         write(fd,out,2);
        
         /*Read in scan codes*/
         temp2 = read(fd,in,1);
        
         /* This is the first number or operator pressed by the user using the LCD */
         if (start == 1)
         {
                /*Initializing indices*/
                indnum = 0;
                indchar = 0;
                ind = 0;
                /*If the numbered entered is a 1*/
                if(in[0] == 'B')
                {
                        sprintf (zero,"%c",'1');
                        TempOperands[indnum] = '1';
                        All[Position] = '1';
                }
                /*If the numbered entered is a 2*/
                else if(in[0] == 'E')
                {
                        sprintf (zero,"%c",'2');
                        TempOperands[indnum] = '2';
                        All[Position] = '2';
                }
                /*If the numbered entered is a 3*/
                else if(in[0] == 'D')
                {
                        sprintf (zero,"%c",'3');
                        TempOperands[indnum] = '3';
                        All[Position] = '3';
                } 
                /*If the numbered entered is a 4*/
                else if(in[0] == 'G')
                {
                        sprintf (zero,"%c",'4');
                        TempOperands[indnum] = '4';
                        All[Position] = '4';
                }
                /*If the numbered entered is a 5*/
                else if(in[0] == 'J')
                {
                        sprintf (zero,"%c",'5');
                        TempOperands[indnum] = '5';
                        All[Position] = '5';
                }
                /*If the numbered entered is a 6*/
                else if(in[0] == 'I')
                {
                        sprintf (zero,"%c",'6');
                        TempOperands[indnum] = '6';
                        All[Position] = '6';
                }
                /*If the numbered entered is a 7*/
                else if(in[0] == 'L')
                {
                        sprintf (zero,"%c",'7');
                        TempOperands[indnum] = '7';
                        All[Position] = '7';
                }
                /*If the numbered entered is a 8*/
                else if(in[0] == 'O')
                {
                        sprintf (zero,"%c",'8');
                        TempOperands[indnum] = '8';
                        All[Position] = '8';
                }
                /*If the numbered entered is a 9*/
                else if(in[0] == 'N')
                {
                        sprintf (zero,"%c",'9');
                        TempOperands[indnum] = '9';
                        All[Position] = '9';
                }
                /*If the numbered entered is a 0*/
                else if(in[0] == 'T')
                {
                        sprintf (zero,"%c",'0');
                        TempOperands[indnum] = '0';
                        All[Position] = '0';
                }
                /*If the operator entered is a + */
                else if(in[0] == 'Q')
                {
                        sprintf (zero,"%c",'+');
                        Oper = '+';
                        TempOperators[indchar] = Oper;
                        All[Position] = Oper;
                }
                /*If the operator entered is a - */
                else if(in[0] == 'S')
                {
                        sprintf (zero,"%c",'-');
                        Oper = '-';
                        TempOperators[indchar] = Oper;
                        All[Position] = Oper;
                }/*If the operator entered is a * */
                else if(in[0] == 'H')
                {
                        sprintf (zero,"%c",'*');
                        Oper = '*';
                        TempOperators[indchar] = Oper;
                        All[Position] = Oper;
                }
                /*If the operator entered is a / */
                else if(in[0] == 'M')
                {
                        sprintf (zero,"%c",'/');
                        Oper = '/';
                        TempOperators[indchar] = Oper;
                        All[Position] = Oper;
                }
                /*If the operator entered is a = */
                else if(in[0] == 'R')
                {
                        sprintf (zero,"%c",'=');
                        Oper = '=';
                        TempOperators[indchar] = Oper;
                        All[Position] = Oper;
                }
                /*If the user wants to clear the screen*/
                else if(in[0] == 'C')
                {
                        clear = 1;
                        Position = -1;
                }
                
                Position = Position + 1;
                ClearScreen();
                
        }
        /* not the first number or Operator that the user has entered*/
        else
        {
                /*User has entered a 1*/
                if(in[0] == 'B')
                {
                        sprintf (zero,"%c",'1');
                        /* If a result is computed and the user enters a number clear all and start a new computation*/
                        /*This code apears for numbers 0-9 */
                        if (All[Position-1] == '$')
                        {
                                ClearScreen();
                                
                                for(i=0; i<50; i++)
                                        Operands[i] = -1;
                                        
                                for(i=0; i<50; i++)
                                        NewOperands[i] = -1;
        
                                for(i=0; i<50; i++)
                                        TempOperands1[i] = -1;
        
                                for(i=0; i<50; i++)
                                        Operators[i] = '$';
                
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                        
                                for(i=0; i<50; i++)
                                        TempOperators[i] = '$';
                        
                                for(i=0; i<200; i++)
                                        All[i] = '$';   
                                
                                number = -1;
                                start = 1;
                                Result = 1000000.0;
                                
                                Position = 0;
                        }
                        indnum = indnum + 1;
                        TempOperands[indnum] = '1';
                        All[Position] = '1';
                        Position = Position + 1;
                }
                /*User has entered a 2*/
                else if(in[0] == 'E')
                {
                        sprintf (zero,"%c",'2');
                        if (All[Position-1] == '$')
                        {
                                ClearScreen();
                                
                                for(i=0; i<50; i++)
                                        Operands[i] = -1;
                                        
                                for(i=0; i<50; i++)
                                        NewOperands[i] = -1;
        
                                for(i=0; i<50; i++)
                                        TempOperands1[i] = -1;
        
                                for(i=0; i<50; i++)
                                        Operators[i] = '$';
                
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                        
                                for(i=0; i<50; i++)
                                        TempOperators[i] = '$';
                        
                                for(i=0; i<200; i++)
                                        All[i] = '$';   
                                
                                number = -1;
                                start = 1;
                                Result = 1000000.0;
                                
                                Position = 0;
                        }
                        indnum = indnum + 1;
                        TempOperands[indnum] = '2';
                        All[Position] = '2';
                        Position = Position + 1;
                }
                /*User has entered a 3*/
                else if(in[0] == 'D')
                {
                        sprintf (zero,"%c",'3');
                        if (All[Position-1] == '$')
                        {
                                ClearScreen();
                                
                                for(i=0; i<50; i++)
                                        Operands[i] = -1;
                                        
                                for(i=0; i<50; i++)
                                        NewOperands[i] = -1;
        
                                for(i=0; i<50; i++)
                                        TempOperands1[i] = -1;
        
                                for(i=0; i<50; i++)
                                        Operators[i] = '$';
                
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                        
                                for(i=0; i<50; i++)
                                        TempOperators[i] = '$';
                        
                                for(i=0; i<200; i++)
                                        All[i] = '$';   
                                
                                number = -1;
                                start = 1;
                                Result = 1000000.0;
                                
                                Position = 0;
                        }
                        indnum = indnum + 1;
                        TempOperands[indnum] = '3';
                        All[Position] = '3';
                        Position = Position + 1;
                }
                /*User has entered a 4*/
                else if(in[0] == 'G')
                {
                        sprintf (zero,"%c",'4');
                        if (All[Position-1] == '$')
                        {
                                ClearScreen();
                                
                                for(i=0; i<50; i++)
                                        Operands[i] = -1;
                                        
                                for(i=0; i<50; i++)
                                        NewOperands[i] = -1;
        
                                for(i=0; i<50; i++)
                                        TempOperands1[i] = -1;
        
                                for(i=0; i<50; i++)
                                        Operators[i] = '$';
                
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                        
                                for(i=0; i<50; i++)
                                        TempOperators[i] = '$';
                        
                                for(i=0; i<200; i++)
                                        All[i] = '$';   
                                
                                number = -1;
                                start = 1;
                                Result = 1000000.0;
                                
                                Position = 0;
                        }
                        indnum = indnum + 1;
                        TempOperands[indnum] = '4';
                        All[Position] = '4';
                        Position = Position + 1;
                }
                /*User has entered a 5*/
                else if(in[0] == 'J')
                {
                        sprintf (zero,"%c",'5');
                        if (All[Position-1] == '$')
                        {
                                ClearScreen();
                                
                                for(i=0; i<50; i++)
                                        Operands[i] = -1;
                                        
                                for(i=0; i<50; i++)
                                        NewOperands[i] = -1;
        
                                for(i=0; i<50; i++)
                                        TempOperands1[i] = -1;
        
                                for(i=0; i<50; i++)
                                        Operators[i] = '$';
                
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                        
                                for(i=0; i<50; i++)
                                        TempOperators[i] = '$';
                        
                                for(i=0; i<200; i++)
                                        All[i] = '$';   
                                
                                number = -1;
                                start = 1;
                                Result = 1000000.0;
                                
                                Position = 0;
                        }
                        indnum = indnum + 1;
                        TempOperands[indnum] = '5';
                        All[Position] = '5';
                        Position = Position + 1;
                }
                /*User has entered a 6*/
                else if(in[0] == 'I')
                {
                        sprintf (zero,"%c",'6');
                        if (All[Position-1] == '$')
                        {
                                ClearScreen();
                                
                                for(i=0; i<50; i++)
                                        Operands[i] = -1;
                                        
                                for(i=0; i<50; i++)
                                        NewOperands[i] = -1;
        
                                for(i=0; i<50; i++)
                                        TempOperands1[i] = -1;
        
                                for(i=0; i<50; i++)
                                        Operators[i] = '$';
                
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                        
                                for(i=0; i<50; i++)
                                        TempOperators[i] = '$';
                        
                                for(i=0; i<200; i++)
                                        All[i] = '$';   
                                
                                number = -1;
                                start = 1;
                                Result = 1000000.0;
                                
                                Position = 0;
                        }
                        indnum = indnum + 1;
                        TempOperands[indnum] = '6';
                        All[Position] = '6';
                        Position = Position + 1;
                        
                }
                /*User has entered a 7*/
                else if(in[0] == 'L')
                {
                        sprintf (zero,"%c",'7');
                        if (All[Position-1] == '$')
                        {
                                ClearScreen();
                                
                                for(i=0; i<50; i++)
                                        Operands[i] = -1;
                                        
                                for(i=0; i<50; i++)
                                        NewOperands[i] = -1;
        
                                for(i=0; i<50; i++)
                                        TempOperands1[i] = -1;
        
                                for(i=0; i<50; i++)
                                        Operators[i] = '$';
                
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                        
                                for(i=0; i<50; i++)
                                        TempOperators[i] = '$';
                        
                                for(i=0; i<200; i++)
                                        All[i] = '$';   
                                
                                number = -1;
                                start = 1;
                                Result = 1000000.0;
                                
                                Position = 0;
                        }
                        indnum = indnum + 1;
                        TempOperands[indnum] = '7';
                        All[Position] = '7';
                        Position = Position + 1;
                }
                /*User has entered a 8*/
                else if(in[0] == 'O')
                {
                        sprintf (zero,"%c",'8');
                        if (All[Position-1] == '$')
                        {
                                ClearScreen();
                                
                                for(i=0; i<50; i++)
                                        Operands[i] = -1;
                                        
                                for(i=0; i<50; i++)
                                        NewOperands[i] = -1;
        
                                for(i=0; i<50; i++)
                                        TempOperands1[i] = -1;
        
                                for(i=0; i<50; i++)
                                        Operators[i] = '$';
                
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                        
                                for(i=0; i<50; i++)
                                        TempOperators[i] = '$';
                        
                                for(i=0; i<200; i++)
                                        All[i] = '$';   
                                
                                number = -1;
                                start = 1;
                                Result = 1000000.0;
                                
                                Position = 0;
                        }
                        indnum = indnum + 1;
                        TempOperands[indnum] = '8';
                        All[Position] = '8';
                        Position = Position + 1;
                }
                /*User has entered a 9*/
                else if(in[0] == 'N')
                {
                        sprintf (zero,"%c",'9');
                        if (All[Position-1] == '$')
                        {
                                ClearScreen();
                                
                                for(i=0; i<50; i++)
                                        Operands[i] = -1;
                                        
                                for(i=0; i<50; i++)
                                        NewOperands[i] = -1;
        
                                for(i=0; i<50; i++)
                                        TempOperands1[i] = -1;
        
                                for(i=0; i<50; i++)
                                        Operators[i] = '$';
                
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                        
                                for(i=0; i<50; i++)
                                        TempOperators[i] = '$';
                        
                                for(i=0; i<200; i++)
                                        All[i] = '$';   
                                
                                number = -1;
                                start = 1;
                                Result = 1000000.0;
                                
                                Position = 0;
                        }
                        indnum = indnum + 1;
                        TempOperands[indnum] = '9';
                        All[Position] = '9';
                        Position = Position + 1;
                }
                /*User has entered a 0*/
                else if(in[0] == 'T')
                {
                        sprintf (zero,"%c",'0');
                        if (All[Position-1] == '$')
                        {
                                ClearScreen();
                                
                                for(i=0; i<50; i++)
                                        Operands[i] = -1;
                                        
                                for(i=0; i<50; i++)
                                        NewOperands[i] = -1;
        
                                for(i=0; i<50; i++)
                                        TempOperands1[i] = -1;
        
                                for(i=0; i<50; i++)
                                        Operators[i] = '$';
                
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                        
                                for(i=0; i<50; i++)
                                        TempOperators[i] = '$';
                        
                                for(i=0; i<200; i++)
                                        All[i] = '$';   
                                
                                number = -1;
                                start = 1;
                                Result = 1000000.0;
                                
                                Position = 0;
                        }
                        indnum = indnum + 1;
                        TempOperands[indnum] = '0';
                        All[Position] = '0';
                        Position = Position + 1;
                }
                /*User has entered a + */
                else if(in[0] == 'Q')
                {
                        sprintf (zero,"%c",'+');
                        indchar = indchar + 1;
                        Oper = '+';
                        /*If a number was entered before this operator then store this operator in the TempOperators array */
                        /*This code is the same for all operators */
                        if((All[Position-1] != '-') && (All[Position-1] != '*') && 
                        (All[Position-1] != '/') && (All[Position-1] != '+'))
                        {
                                TempOperators[indchar] = Oper;
                        }
                        /*If an operator was entered before this operator then store this operator in place if it in TempOperators array*/
                        /*This code is the same for all operators */
                        if((All[Position-1] == '-') || (All[Position-1] == '*') || 
                        (All[Position-1] == '/') || (All[Position-1] == '+'))
                        {
                                indchar = indchar - 1;
                                TempOperators[indchar] = Oper;
                                /*Go to Position: Column c Row r */
                                c = c - 1;
                                sprintf (out, "%cG%c%c", 254, c, r);
                                write(fd,out,4);
                                
                        }
                        /*If a number was entered before this operator then store this operator convert string to an int and store it */
                        /*This code is the same for all operators */
                        if((All[Position-1] != '-') && (All[Position-1] != '*') && 
                        (All[Position-1] != '/') && (All[Position-1] != '+'))
                        {
                                p_array = TempOperands;
                                number = atoi(TempOperands);
                                TempOperands1[ind] = number;
                                ind = ind + 1;
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                indnum = 0;
                        }
                        All[Position] = '+';
                        Position = Position + 1;
                }
                /*User has entered a - */
                else if(in[0] == 'S')
                {
                        sprintf (zero,"%c",'-');
                        indchar = indchar + 1;
                        Oper = '-';
                        if((All[Position-1] != '-') && (All[Position-1] != '*') && 
                        (All[Position-1] != '/') && (All[Position-1] != '+'))
                        {
                                TempOperators[indchar] = Oper;
                        }
                        if((All[Position-1] == '*') || (All[Position-1] == '+') || 
                        (All[Position-1] == '/') || (All[Position-1] == '-'))
                        {
                                indchar = indchar - 1;
                                TempOperators[indchar] = Oper;
                                /*Go to Position: Column c Row r */
                                c = c - 1;
                                sprintf (out, "%cG%c%c", 254, c, r);
                                write(fd,out,4);
                        }
                        if((All[Position-1] != '-') && (All[Position-1] != '*') && 
                        (All[Position-1] != '/') && (All[Position-1] != '+'))
                        {
                                p_array = TempOperands;
                                number = atoi(TempOperands);
                                if(Position == 0)
                                {
                                        if (All[0] == '-')
                                                number = -number;
                                }
                                TempOperands1[ind] = number;
                                ind = ind + 1;
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                indnum = 0;
                        }
                        All[Position] = '-';
                        Position = Position + 1;
                        
                }
                /*User has entered a * */
                else if(in[0] == 'H')
                {
                        sprintf (zero,"%c",'*');
                        indchar = indchar + 1;
                        Oper = '*';
                        if((All[Position-1] != '-') && (All[Position-1] != '*') && 
                        (All[Position-1] != '/') && (All[Position-1] != '+'))
                        {
                                TempOperators[indchar] = Oper;
                        }
                        if((All[Position-1] == '-') || (All[Position-1] == '+') || 
                        (All[Position-1] == '/') || (All[Position-1] == '*'))
                        {
                                indchar = indchar - 1;
                                TempOperators[indchar] = Oper;
                                /*Go to Position: Column c Row r */
                                c = c - 1;
                                sprintf (out, "%cG%c%c", 254, c, r);
                                write(fd,out,4);
                        }
                        if((All[Position-1] != '-') && (All[Position-1] != '*') && 
                        (All[Position-1] != '/') && (All[Position-1] != '+'))
                        {
                                p_array = TempOperands;
                                number = atoi(TempOperands);
                                TempOperands1[ind] = number;
                                ind = ind + 1;
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                indnum = 0;
                        }
                        All[Position] = '*';
                        Position = Position + 1;
                }
                /*User has entered a / */
                else if(in[0] == 'M')
                {       
                        sprintf (zero,"%c",'/');
                        indchar = indchar + 1;
                        Oper = '/';
                        if((All[Position-1] != '-') && (All[Position-1] != '*') && 
                        (All[Position-1] != '/') && (All[Position-1] != '+'))
                        {
                                TempOperators[indchar] = Oper;
                        }
                        if((All[Position-1] == '-') || (All[Position-1] == '+') || 
                        (All[Position-1] == '*') || (All[Position-1] == '/'))
                        {
                                indchar = indchar - 1;
                                TempOperators[indchar] = Oper;
                                /*Go to Position: Column c Row r */
                                c = c - 1;
                                sprintf (out, "%cG%c%c", 254, c, r);
                                write(fd,out,4);
                        }
                        if((All[Position-1] != '-') && (All[Position-1] != '*') && 
                        (All[Position-1] != '/') && (All[Position-1] != '+'))
                        {
                                p_array = TempOperands;
                                number = atoi(TempOperands);
                                TempOperands1[ind] = number;
                                ind = ind + 1;
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                indnum = 0;
                        }
                        All[Position] = '/';
                        Position = Position + 1;
                }
                /*User has entered a = */
                else if(in[0] == 'R')
                {
                        sprintf (zero,"%c",'=');
                        indchar = indchar + 1;
                        Oper = '=';
                        if((All[Position-1] != '-') && (All[Position-1] != '*') && 
                        (All[Position-1] != '/') && (All[Position-1] != '+'))
                        {
                                TempOperators[indchar] = Oper;
                        }
                        if((All[Position-1] == '-') || (All[Position-1] == '+') || 
                        (All[Position-1] == '*') || (All[Position-1] == '/'))
                        {
                                indchar = indchar - 1;
                                TempOperators[indchar] = Oper;
                                /*Go to Position: Column c Row r */
                                c = c - 1;
                                sprintf (out, "%cG%c%c", 254, c, r);
                                write(fd,out,4);
                        }
                        if((All[Position-1] != '-') && (All[Position-1] != '*') && 
                        (All[Position-1] != '/') && (All[Position-1] != '+'))
                        {
                                p_array = TempOperands;
                                number = atoi(TempOperands);
                                TempOperands1[ind] = number;
                                ind = ind + 1;
                                for(i=0; i<10; i++)
                                        TempOperands[i] = ' ';
                                indnum = 0;
                        }
                        All[Position] = '=';
                        Position = Position + 1;
                }
                /*User would like to clear the LCD */
                else if(in[0] == 'C')
                {
                        clear = 1;
                        Position = -1;
                }
        }

        if (in[0] != nothing[0])
        { 
                /*Write to the LCD screen */
                sprintf(out, "%c",zero[0]);
                write(fd,out,1);
                c++;
                /* Controlling the cursor on the LCD */
                if(c == 21)
                {
                        r++;
                        c = 1;
                        if(r == 5)
                                ClearScreen();
                }
                /*Go to Position: Column c Row r */
                sprintf (out, "%cG%c%c", 254, c, r);
                write(fd,out,4);
        }
         
        start = 0;

}

/* Used to clear the LCD */
void ClearScreen()
{
   row = 1;
   column = 1;
   r = 1;
   c = 1;
        
   /*Clear the LCD Screen */
   sprintf(out, "%cX", 254);
   write(fd,out,2);
   
   /*Clear the buffer */
   sprintf(out, "%cE", 254);
   write(fd,out,2);
}


/* Will write a float (the result) to the LCD*/
void Write_To_LCD(float num)
{

   /*Clear output string for writing */
   for(i = 0; i < 80; i++)
        out[i] = ' ';

   if ((num <= -1000000) && (num > -10000000))
        digits = 12;
   else if ((num <= -100000) && (num > -1000000))
        digits = 11;
   else if ((num <= -10000) && (num > -100000))
        digits = 10;
   else if ((num <= -1000) && (num > -10000))
        digits = 9;
   else if ((num <= -100) && (num > -1000))
        digits = 8;
   else if ((num <= -10) && (num > -100))
        digits = 7;
   else if ((num <= -1 ) && (num > -10)) 
        digits = 6;
   else if ((num < 0 ) && (num > -1)) 
        digits = 5;
   else if ((num > 0 ) && (num < 1)) 
        digits = 5;
   else if ((num >= 1 ) && (num < 10)) 
        digits = 5;
   else if ((num >= 10) && (num < 100))
        digits = 6;
   else if ((num >= 100) && (num < 1000))
        digits = 7;
   else if ((num >= 1000) && (num < 10000))
        digits = 8;
   else if ((num >= 10000) && (num < 100000))
        digits = 9;
   else if ((num >= 100000) && (num < 1000000))
        digits = 10;
   else if ((num >= 1000000) && (num < 10000000))
        digits = 11;
        
   
   row = r+1;
  
   if(row == 5)
   {
        row = 1;
        ClearScreen();
   }
   /*Go to Position: Column 1 Row 1 */
   sprintf (out, "%cG%c%c", 254, column, row);
   write(fd,out,4);
   
   /*Print the Result */
   sprintf (out, "%f", num);
   write(fd,out,digits);
   
   r = row;
   c = digits + 1;

}