Getting string of Data from a keypad in Pic Mikroc

Dear All I have made a simple calculator using pic16F877A in Mikroc. Now I want to improve it. I want to do operations on string instead of single single digit. Like 220*450, 556+778 etc.
earlier its is just for single digit like 4+8, 9-4 etc.
pls help me in this regard and Also I want to make functions of arithmetic operations. Do help me plz.
My Complete code is give below.
// Simple Calculator by Tanvir Ahmad
char txt[2];
int kp;
// Keypad module connections
char keypadPort at PORTD;
// LCD connections definitions
sbit LCD_RS at RB4_bit;
sbit LCD_EN at RB5_bit;
sbit LCD_D4 at RB0_bit;
sbit LCD_D5 at RB1_bit;
sbit LCD_D6 at RB2_bit;
sbit LCD_D7 at RB3_bit;
sbit LCD_RS_Direction at TRISB4_bit;
sbit LCD_EN_Direction at TRISB5_bit;
sbit LCD_D4_Direction at TRISB0_bit;
sbit LCD_D5_Direction at TRISB1_bit;
sbit LCD_D6_Direction at TRISB2_bit;
sbit LCD_D7_Direction at TRISB3_bit;

// MAIN

void main() {


int Calc, Op1, Op2, txt1;
Keypad_Init(); // Initialize Keypad
Lcd_Init(); // Initialize Lcd

Lcd_Cmd(_LCD_CLEAR); // Clear display
Lcd_Cmd(_LCD_CURSOR_OFF); // Cursor off
Lcd_Out(1, 3, "Welcome to"); // Write message text on Lcd
Lcd_Out(2, 8, "UES"); // Write message text on Lcd
delay_ms(2000) ;
Lcd_Cmd(_LCD_CLEAR);
Lcd_Out(1, 5, "Simple"); // Write message text on Lcd
Lcd_Out(2, 3, "Calculator"); // Write message text on Lcd
delay_ms(3000) ;
Lcd_Cmd(_LCD_CLEAR);


start:
Lcd_Cmd(_LCD_CLEAR);
Lcd_Out(1, 1, "Key1:"); // Write message text on Lcd
Lcd_Out(2, 1, "Key2:"); // Write message text on Lcd
Lcd_Out(1,12, "k3:");


while(1){
kp = 0; // Reset key code variable

do
kp = Keypad_Key_Click(); // Store key code in kp variable
while (!kp);

switch (kp) {
case 9: kp = 49; break; // 1
case 10: kp = 50; break; // 2
case 11: kp = 51; break; // 3
case 5: kp = 52; break; // 4
case 6: kp = 53; break; // 5
case 7: kp = 54; break; // 6
case 1: kp = 55; break; // 7
case 2: kp = 56; break; // 8
case 3: kp = 57; break; // 9
case 14: kp = 48; break; // 0
}
Lcd_Chr(1, 8, kp);
delay_ms(200);

{
op1 = 0; // Reset key code variable
do
op1 = Keypad_Key_Click(); // Store key code in kp variable
while (!op1);
switch (op1) {
case 9: op1 = 49; break; // 1
case 10: op1 = 50; break; // 2
case 11: op1 = 51; break; // 3
// case 4: op1 = 47; break; // /
case 5: op1 = 52; break; // 4
case 6: op1 = 53; break; // 5
case 7: op1 = 54; break; // 6
case 1: op1 = 55; break; // 7
case 2: op1 = 56; break; // 8
case 3: op1 = 57; break; // 9
case 14: op1 = 48; break; // 0





}
Lcd_Chr(2, 8, op1);
}
{
op2=0;
do
op2 = Keypad_Key_Click(); // Store key code in kp variable
while (!op2);
switch (op2) {
case 16: Op2= 43; break; // +
case 12: Op2= 45; break; // -
case 8: Op2= 42; break; // *
case 4: Op2= 47; break; // /
//case 15: Op2= 61; break; // =
}
Lcd_Chr(2, 12, op2);
//Addition
if (op2==43) {
Op1 = Op1-48;
kp = kp-48;
calc = kp+op1;

intToStr(calc, txt); // Transform Calc value to string
Lcd_Cmd(_LCD_CLEAR); // Clear display
Lcd_Out(1,2, " Result is :");
Lcd_Out(2, 10, txt); // Display Calc value on Lcd
}
// Subtraction
if (op2==45) {
Op1 = Op1-48;
kp = kp-48;
calc = kp-op1;
if(op1>kp){
Calc=Op1-kp ;
Lcd_Cmd(_LCD_CLEAR);
Lcd_Out(2,9,"-");
WordToStr(calc, txt); // Transform Calc value to string
// Lcd_Cmd(_LCD_CLEAR); // Clear display
Lcd_Out(1,2, " Result is :");
Lcd_Out(2, 10, txt);
delay_ms(1200);
Lcd_Cmd(_LCD_CLEAR);
goto start;
}
WordToStr(calc, txt); // Transform Calc value to string
Lcd_Cmd(_LCD_CLEAR); // Clear display
Lcd_Out(1,2, " Result is :");
Lcd_Out(2, 10, txt); // Display Calc value on Lcd
}

// Multiplication
if (op2==42) {
Op1 = Op1-48;
kp = kp-48;
calc = kp*op1;
WordToStr(calc, txt); // Transform Calc value to string
Lcd_Cmd(_LCD_CLEAR); // Clear display
Lcd_Out(1,2, " Result is :");
Lcd_Out(2, 10, txt); // Display Calc value on Lcd
}

// Division
if (op2==47) {
Op1 = Op1-48;
kp = kp-48;
calc = kp/op1;
WordToStr(calc, txt); // Transform Calc value to string
Lcd_Cmd(_LCD_CLEAR); // Clear display
Lcd_Out(1,2, " Result is :");
Lcd_Out(2, 10, txt); // Display Calc value on Lcd
}
delay_ms(1000);
goto start;
}
}
}

Are you saying that your calculator does calculations like 2*2 = 4 and you want to make it does calculations like 10*10 = 100. If yes, you have to use the below code


key gets the value from key press and key is an integer variable. If 1 and then 0 is pressed then value of variable value will be 10. Then if you press an operator like * you have to assign the value of value to another variable operand1 and clear value. Then if the second operand is entered the value of value will be 10 (say) then finally "operand1 (operator) value" is performed when = is pressed.

Dear jayanth.devarayanadurga!
Thanks alot. Yes I want the calculation like 10*10=10. can you further elaborate your code as i am begineer in progarming. I mean can you plz enhance the code for me or make changes in the code which I have proviede.

Thanks alot for your support.