CALCULATOR.CPP

#include<stdio.h>
#include<conio.h>
#include<math.h>
#include<stdlib.h>

#define KEY "Enter the calculator Operation you want to do:"


void addition();
void subtraction();
void multiplication();
void division();
void modulus();
void power();
int factorial();
void calculator_operations();


int main()
{
    int X=1;
    char Calc_oprn;


    calculator_operations();

    while(X)
    {
	printf("\n");
	printf("%s : ", KEY);

	Calc_oprn=getche();

	switch(Calc_oprn)
	{
	    case '+': addition();
		      break;

	    case '-': subtraction();
		      break;

	    case '*': multiplication();
		      break;

	    case '/': division();
		      break;

	    case '?': modulus();
		      break;

	    case '!': factorial();
		      break;

	    case '^': power();
		      break;

	    case 'H':
	    case 'h': calculator_operations();
		      break;

	    case 'Q':
	    case 'q': exit(0);
		      break;
	    case 'c':
	    case 'C': system("cls");
		      calculator_operations();
		      break;

	    default : system("cls");

    printf("\n**********You have entered unavailable option");
    printf("***********\n");
    printf("\n*****Please Enter any one of below available ");
    printf("options****\n");
		      calculator_operations();
	}
    }
}

void calculator_operations()
{

    printf("\n             Welcome to Basic C calculator \n\n");

    printf("* Press 'q' to quit ");
    printf("the program ********\n");
    printf("* Press 'h' to display ");
    printf("below options *****\n\n");
    printf("Enter 'c' to clear the screen and");
    printf(" display available option \n\n");

    printf("Enter + symbol for Addition \n");
    printf("Enter - symbol for Subtraction \n");
    printf("Enter * symbol for Multiplication \n");
    printf("Enter / symbol for Division \n");
    printf("Enter ? symbol for Modulus\n");
    printf("Enter ^ symbol for Power \n");
    printf("Enter ! symbol for Factorial \n\n");
}

void addition()
{
    int n, total=0, k=0, number;
    printf("\nEnter the number of elements you want to add:");
    scanf("%d",&n);
    printf("Please enter %d numbers one by one: \n",n);
    while(k<n)
    {
	scanf("%d",&number);
	total=total+number;
	k=k+1;
    }
    printf("Sum of %d numbers = %d \n",n,total);
}

void subtraction()
{
    int a, b, c = 0;
    printf("\nPlease enter first number  : ");
    scanf("%d", &a);
    printf("Please enter second number : ");
    scanf("%d", &b);
    c = a - b;
    printf("\n%d - %d = %d\n", a, b, c);
}

void multiplication()
{
    int a, b, mul=0;
    printf("\nPlease enter first numb   : ");
    scanf("%d", &a);
    printf("Please enter second number: ");
    scanf("%d", &b);
    mul=a*b;
    printf("\nMultiplication of entered numbers = %d\n",mul);
}

void division()
{
    int a, b, d=0;
    printf("\nPlease enter first number  : ");
    scanf("%d", &a);
    printf("Please enter second number : ");
    scanf("%d", &b);
    d=a/b;
    printf("\nDivision of entered numbers=%d\n",d);
}

void modulus()
{
    int a, b, d=0;
    printf("\nPlease enter first number   : ");
    scanf("%d", &a);
    printf("Please enter second number  : ");
    scanf("%d", &b);
    d=a%b;
    printf("\nModulus of entered numbers = %d\n",d);
}

void power()
{
    double a,num, p;
    printf("\nEnter two numbers to find the power \n");
    printf("number: ");
    scanf("%lf",&a);

    printf("power : ");
    scanf("%lf",&num);

    p=pow(a,num);

    printf("\n%lf to the power %lf = %lf \n",a,num,p);
}

int factorial()
{
    int i,fact=1,num;

    printf("\nEnter a number to find factorial : ");
    scanf("%d",&num);

    if (num<0)
    {
	printf("\nPlease enter a positive number to");
	printf(" find factorial and try again. \n");
	printf("\nFactorial can't be found for negative");
	printf(" values. It can be only positive or 0  \n");
	return 1;
    }

    for(i=1;i<=num;i++)
    fact=fact*i;
    printf("\n");
    printf("Factorial of entered number %d is:%d\n",num,fact);
    return 0;
}