simple while loop calculator

Question

Hello im stuck at SUBTRACTION AND DIVITION AND I CANT FIGURE OUT WHAT CODE to use because when I try to subtract 10 i inputed it then it will loop since the while condition is not meet which it needs to be negative to terminate the loop and i inputed 2 for the second number then loop again then i putted -number which lead to terminate loop and subtract all the number but the result is -12 its always wrong in every number cant figure out why Please help Also with divition, only my addition is working havent started the divition cuz i cant figure out how

#include <iostream>
using namespace std;
                        
int  amt2, total;
double subNumbers();
double amt=1;
double number=0;
int main() {
int chc=0;
    int amt = 0;
    int amt2 = 1;
    
    cout << "Welcome again User!\n";
    cout << "______________________________________________________________\n" << endl;
    cout << "Mathematical Operations(Improved):\n\n";
    
    cout << "\t[1]-Addition" << endl;
    cout << "\t[2]-Subtraction" << endl;    
    cout << "\t[3]-Multiplication" << endl;
    cout << "\t[4]-Division\n" << endl;    
    
    cout << "______________________________________________________________\n" << endl;
    
    cout << "Type the number corresponding to your chosen operation: ";
    cin >> chc;
```
  switch (chc) {    
  case 1:
``` 
    system ("cls");
    
    cout << "\n\n\tOperation chosen: Addition";
    
    cout << "\n______________________________________________________________" << endl;
    
    cout << "\n\nInput positive numbers to use the operation and input a negative number to end the operation.\n\n";
    
    cout << "Enter your number: ";`
    cin >> number;
    
    while (number >= 0) {
        // add all positive numbers
        amt += number;
        
        // take input again if the number is positive
        cout << "Enter another number: ";
        cin >> number;
    }
    
        // display the sum
    cout << "\nThe sum of all the numbers is: " << amt << endl;
    break; 
```
  case 2:  
    system ("cls");
    cout << "\n\n\tOperation chosen: Subtraction";
    

  
    cout << "\n______________________________________________________________" << endl;
    
    cout << "\n\nInput positive numbers to use the operation and input a negative number to end the operation.\n\n";
    do{
    
    cout << "Enter your number: ";
    cin >> number;
    amt=number-number ; 


  

    
    }while (number >= 0);// subtract all positive numbers
      
        
    
    
        // display the difference
    cout << "\nThe difference of all the numbers is: "<<amt;
return 0;
   
    
   

}}

   

``` 

    enter code here

Answer 1

You are subtracting number from number:

amt = number - number; // Which is always 0

So that's why amt == 0 always.

So just change your loop to this:

while (true) {

    cout << "Enter your number: ";
    cin >> number;

    if (number < 0) break;

    if (amt == 0) amt = number;
    else if (number >= 0) amt -= number;
}

What this does is that if amt == 0, then set amt to number. I have done this because as the default value of amt is 0 (due to int amt = 0;), when amt == 0, then we can assume that the user has entered the first number, and thus we can set amt to number. And then we can use -= operator, which basically means:

amt = amt - number;

But before all this, using if (number < 0) break; we can check if the user has entered a negative number, and if the user has entered a negative number, then the break keyword will break out of the while loop.