why this doesn't work with char ?

[T4l0n]

i made a simple calculator using floats and string:

#include <iostream>
#include <string>
using namespace std;

float add(float num1, float num2){
      return num1+num2;
      }

float sub(float num1, float num2){
      return num1-num2;
      }
      
float mol(float num1, float num2){
      return num1*num2;
      }
      
float div(float num1, float num2){
      return num1/num2;
      }
      
int main (){
    string input;
    float num1;
    float num2;
    cin >> num1;
    do{
        cin >> input;
        if(input=="+"){
                       cin >> num2;
                       cout << add(num1, num2) << endl;
                       }
        else if(input=="-"){
                       cin >> num2;
                       cout << sub(num1, num2) << endl;
                       }
        else if(input=="*"){
                       cin >> num2;
                       cout << mol(num1, num2) << endl;
                       }
        else if(input=="/"){
                       cin >> num2;
                       cout << div(num1, num2) << endl;
                       }
        else{
             cout << "decide to add, sub, molt or div" << endl;
             }}
        while(input!="+" & input!="-" & input!="*" & input!="/"); 
    system("pause");
    return 0;
}

This properly works, but if i try to change string input at line22 with for example char input [50] i always got else (cout << "decide to add, sub, molt or div" << endl;) after cin >> input. Can anyone explain me why this happens ?
thanks

[Lynx876]

You'd also need to change the if statements to check for a char literal:
if( input == '+' )

Note, the single quotes, not double.

Double quotes, would be checking for a char *.