C++ calling different methods if char is entered - c++

Question

Hello I'm trying to create a console application that allows the user to input a single character to preform an arithmetic operation.
Currently the program only adds the two numbers together even if I input an m, meaning multiply. I believe it is going straight into the first if statement for some reason even if I dont want addition.
#include <iostream>
using namespace std;
int add(int a, int b)
{
int c;
c = a + b;
return c;
}
int subtract(int a, int b)
{
int c;
c = a - b;
return c;
}
int multiply(int a, int b)
{
int c;
c = a * b;
return c;
}
int divide(int a, int b)
{
int c;
c = a / b;
return c;
}
int remainder(int a, int b)
{
int c;
c = a % b;
return c;
}
int main ()
{
int a;
int b;
char op;
cout << "****************Integer Calculator**************** " << endl << "Press enter to continue." << endl;
cout << "Enter the first integer: " << endl;
cin >> a;
cout << "Enter the second integer: " << endl;
cin >> b;
cout << "What operation would you like to perform? Enter a single character " << endl << "Add - A , a or + " << endl <<
"Subtract - S , s or - " << endl << "Multiply - M , m or * " << endl << "Divide - D , d or / " << endl << "Remainder - R , r or % " << endl;
cin >> op;
if (op ='A' || 'a' || '+')
{
int answer1 = 0;
answer1 = add(a, b);
cout << "The answer is: " << answer1 << endl;
system("PAUSE");
return 0;
}
else if(op == 'S' || 's' || '-')
{
int answer2 = 0;
answer2 = subtract(a, b);
cout << "The answer is: " << answer2 << endl;
system("PAUSE");
return 0;
}
else if (op == 'M' || 'm' || '*')
{
int answer3 = 0;
answer3 = multiply(a, b);
cout << "The answer is: " << answer3 << endl;
system("PAUSE");
return 0;
}
else if (op == 'D' || 'd' || '/')
{
int answer4 = 0;
answer4 = divide(a, b);
cout << "The answer is: " << answer4 << endl;
system("PAUSE");
return 0;
}
else if (op == 'R' || 'r' || '%')
{
int answer5 = 0;
answer5 = remainder(a, b);
cout << "The answer is: " << answer5 << endl;
system("PAUSE");
return 0;
}

Answer 1

Your logic is incorrect, and you are using the assignment operator to boot.
if (op ='A' || 'a' || '+')
This should be:
if (op == 'A' || op == 'a' || op == '+')
Usually for stuff like this we use a switch:
switch( toupper(op) )
{
case 'A':
case '+':
// Do adding...
break;
case 'S':
case '-':
// Do subtraction...
break;
// etc...
default:
cout << "Unknown operation : " << op << endl;
}

Answer 2

In your if statement
(op ='A' || 'a' || '+')
you are not testing if op equals 'A'. You are setting op equal to 'A', and then testing if 'a' and '+' are true, which they are. To fix this, use the == operator, and test op for every case like so:
if (op == 'A' || op == 'a' || op == '+')...
else if(op == 'S' || op == 's' || op == '-')...
// and so on