More Function Malfunction

[Randeh]

Newb C++ problem, arithmetic functions are returning 0 values each time. Not sure where the problem is, but I've run checks and it seems to be going fine until the very end where the arithmetic functions are:

#include <iostream>
#include <iomanip>
#include <cstring>
using namespace std;

const int SIZE = 41;
char TestOp, UseOp, TestNum[SIZE];
double UseNum, result, value;
int i, j;

void introduction();
bool IsValidOp(char TestOp, int i);
bool IsValidNum(char TestNum[], int j);
double Addition(double UseNum, double result);
double Subtraction(double UseNum, double result);
double Division(double UseNum, double result);
double Multiplication(double UseNum, double result);

void main()
     {
     introduction();
     result = 0;
          while (1) 
	{							cout << "Enter desired operation: ";
	cin >> TestOp;

	if (IsValidOp(TestOp, i))	
	     UseOp = TestOp;
	else
	     {
	     cout << "Invalid operator. Try again." << endl;
	     continue;
	     } 

	switch(UseOp)
	     {
	     case 'C':
	     case 'c': 
                          cout << "Result has been reset to 0." << endl;
	          continue;
		
	     case 'X': 
	     case 'x': break;
	     }

	cout << "Enter a number: ";
	cin >> TestNum;
		
	if (IsValidNum(TestNum, j))
	     UseNum = atof(TestNum);
	else {
	      cout << "Invalid number. Try again." << endl;
	      continue;
	       }
		
	switch (UseOp)
	     {
	     case '+': result = Addition(UseNum, result);
                     case '-': result = Subtraction(UseNum, result);
	     case '*': result = Multiplication(UseNum, result);
                     case '/': 
		if (UseOp=='/' && UseNum==0)
		{
	               cout << "Error: Cannot divide by zero. Try again." << endl;
		continue;
		}
		else{
		       result = Division(UseNum, result);
		      }
	
                cout << "Result: " << result << endl;
		}
	}
}

//Function for introduction to the program
void introduction()
{
cout << "-------------------------------------------------------------------------------" << endl;
cout << "This program will act as a basic four-function calculator. The valid operators\nare + for addition, - for subtraction, * for multiplication, and / for division.Typing a C or c as an operator will clear the result and restart the calculator.Typing an X or x as an operator will shut down the program and end the\ncalculator. All numbers will be displayed as whole numbers." << endl;
cout << "-------------------------------------------------------------------------------" << endl;
	}

//Function to read the operator, validate it, and store it
bool IsValidOp(char TestOp, int i)
	{
	char ValidOp[9] = "+-*/cCxX";
	for (i=0; i<9; i++)
		{
		if (TestOp==ValidOp[i])
			return true;
		}
	return false;
	}

//Function to validate the numbers
bool IsValidNum(char TestNum[], int j)
	{
	for (j=0; j<41; j++)
		{
		if (isdigit(TestNum[j]) || TestNum[j]=='.')
			{
			return true;
			break;
			}
		}
	return false;
	}

//Operational functions
double Addition(double UseNum, double result)
	{
	return result + UseNum;
	}

double Subtraction(double UseNum, double result)
	{
	return result - UseNum;
	}

double Multiplication(double UseNum, double result)
	{
	return result * UseNum;
	}

double Division(double UseNum, double result)
	{
	return result = (result / UseNum); 
	}

[horace1]

you need to have a break; after each operation in your switch statement, e.g.

	switch (UseOp)
	     {
	     case '+': result = Addition(UseNum, result);
                         cout << "Result: " << result << endl;break;
                     case '-': result = Subtraction(UseNum, result);cout << "Result: " << result << endl;break;
	     case '*': result = Multiplication(UseNum, result);cout << "Result: " << result << endl;break;
                     case '/': 
		if (UseOp=='/' && UseNum==0)
		{
	               cout << "Error: Cannot divide by zero. Try again." << endl;
		continue;
		}
		else{
		       result = Division(UseNum, result);
		      }
	
                cout << "Result: " << result << endl;
		}
	}