My program will loop regardless of whatever char I enter - c++

Question

I have been working on a very very basic calculation program in C++. It calculates the square root of a number, and also squares it if the user wants. This is what I have so far (I know it's probably rubbish code, but I'm a beginner just experimenting to see how it all works. Any suggestions greatly appreciated though):
#include <iostream>
#include <stdlib.h>
#include <math.h>
using namespace std;
int number; // Global variables to be used in void functions as well as main.
int squaredNumber;
double sqrtResult;
char input;
char useAgain;
void squareNum(); // Prototypes for the void functions
void sqrtNum();
void useAgainQuery();
int main()
{
retry: // Establishing somewhere to send user if their input is invalid.
system("cls");
cout << "Square Calcualtions" << endl;
cout << "******************" << endl;
cout << endl;
cout << "Do you want to square a number or find the square root of a number?" << endl;
cout << "Please select 1 or 2 respectively." << endl;
cout << endl;
cin >> input;
if (input == '1')
{
cout << "Please press ENTER to continue." << endl;
cin.ignore().get();
squareNum(); // If the input is 1, run the void to square a number.
}
else if (input == '2')
{
cout << "Please press ENTER to continue." << endl;
cin.ignore().get();
sqrtNum(); // If the input is 2, run the void to sqrt a number.
}
else if (input != '1' || '2')
{
system("cls");
cout << "Square Calcualtions" << endl;
cout << "******************" << endl;
cout << endl;
cout << "Your selection was invalid, please enter 1 or 2." << endl;
cin.ignore().get();
goto retry; // If the input isn't either 1 or 2, send back to the start of program.
}
return 0;
}
void squareNum() // function to square the inputted number.
{
system("cls");
cout << "Square Calcualtions" << endl;
cout << "******************" << endl;
cout << endl;
cout << "Enter the number you want to square." << endl;
cin >> number;
cout << "You have chosen: " << number << endl;
cout << "Press ENTER to calculate." << endl;
cin.ignore().get();
system("cls");
squaredNumber = number * number; // Simple maths to find the square number
cout << "You have squared " << number << "." << endl;
cout << "The result was " << squaredNumber << "." << endl;
cout << "Press ENTER to continue." << endl;
cin.get();
useAgainQuery();
return;
}
void sqrtNum()
{
system("cls");
cout << "Square Calcualtions" << endl;
cout << "******************" << endl;
cout << endl;
cout << "Enter the number you would like the square root of." << endl;
cin >> number;
cout << "You have chosen: " << number << "." << endl;
cout << "Press ENTER to calculate." << endl;
cin.ignore().get();
system("cls");
sqrtResult = sqrt(number);
cout << "You have found the square root of " << number << "." << endl;
cout << "The result was: " << sqrtResult << "." << endl;
cout << "Press ENTER to continue." << endl;
cin.get();
useAgainQuery();
return;
}
void useAgainQuery()
{
system("cls");
cout << "Square Calcualtions" << endl;
cout << "******************" << endl;
cout << endl;
cout << "Would you like to make another calculation?" << endl;
cout << "Y for Yes and N for No." << endl;
cout << endl;
cin >> useAgain;
if (useAgain == 'Y' || 'y')
{
retry2: // Establishing somewhere to send user if their input is invalid.
system("cls");
cout << "Square Calcualtions" << endl;
cout << "******************" << endl;
cout << endl;
cout << "Do you want to square a number or find the square root of a number?" << endl;
cout << "Please select 1 or 2 respectively." << endl;
cout << endl;
cin >> input;
if (input == '1')
{
cout << "Please press ENTER to continue." << endl;
cin.ignore().get();
squareNum(); // If the input is 1, run the void to square a number.
}
else if (input == '2')
{
cout << "Please press ENTER to continue." << endl;
cin.ignore().get();
sqrtNum(); // If the input is 2, run the void to sqrt a number.
}
else if (input != '1' || '2')
{
system("cls");
cout << "Square Calcualtions" << endl;
cout << "******************" << endl;
cout << endl;
cout << "Your selection was invalid, please enter 1 or 2." << endl;
cin.ignore().get();
goto retry2;
}
}
else if (useAgain != 'Y' || 'y')
return;
return;
}
So yeah, when I go through and it asks "Would you like to play again", it goes through it over and over. It doesn't matter what key I press but it loops. Any help would be greatly appreciated!

Answer 1

Change your condition here:
if (useAgain == 'Y' || 'y')
to
if (useAgain == 'Y' || useAgain=='y')
Also, change this:
else if (useAgain != 'Y' || 'y')
{
return;
}
to this:
else if (useAgain != 'Y' && useAgain!='y')
{
return;
}

Answer 2

Perhaps try creating a bool variable that controls the entire main loop, like this:
#include <InsertLibrariesHere>
int main(){
bool running=true;
while(running){
//calculations here
//continue(Y/N)?
if (input == N || input == n){running = false;}
}
}

Answer 3

Don't use goto, use a while(1) instead.
your last if statement is wrong, it needs to be
if (input != '1' && input != '2')

Answer 4

You can simplify your comparisons to letters:
if (std::toupper(useAgain) == 'Y')
or
if (std::tolower(useAgain) == 'y')
You can also convert the case after you input:
cin >> useAgain;
useAgain = std::toupper(useAgain);
if (useAgain == 'Y')
There is also std::transform is you need to transform a std::string to all lower or all upper case.