assignmen 3-2 - binary3.cpp

this code is code c++. have many lesson

#include<iostream>
#include<string>

using namespace std;
int main()
{
    string input,output = "",output2 = "";
    
    cout << "Enter a number (in Hexadecimal): " ;
	cin >> input;
	
    for(int i=0;i<4;i++)
    {
            if(input.at(i)== '0')
            {
             output += "0000";
             output2 += "0000";
            }
            if(input.at(i)== '1')
            {
             output += "0001";
             output2 += "0001";
            }
            if(input.at(i)== '2')
            {
             output += "0010";
             output2 += "0010";
            }
            if(input.at(i)== '3')
            {
             output += "0011";
             output2 += "0011";
            }
            if(input.at(i)== '4')
            {
             output += "0100";
             output2 += "0100";
            }
            if(input.at(i)== '5')
            {
             output += "0101";
             output2 += "0101";
            }
            if(input.at(i)== '6')
            {
             output += "0110";
             output2 += "0110";
            }
            if(input.at(i)== '7')
            {
             output += "0111";
             output2 += "0111";
            }
            if(input.at(i)== '8')
            {
             output += "1000";
             output2 += "1000";
            }
            if(input.at(i)== '9')
            {
             output += "1001";
             output2 += "1001";
            }
            if(input.at(i)== 'A')
            {
             output += "1010";
             output2 += "1010";
            }
            if(input.at(i)== 'B')
            {
             output += "1011";
             output2 += "1011";
            }
            if(input.at(i)== 'C')
            {
             output += "1100";
             output2 += "1100";
            }
            if(input.at(i)== 'D')
            {
             output += "1101";
             output2 += "1101";
            }
            if(input.at(i)== 'E')
            {
             output += "1110";
            output2 += "1110";
            }
            if(input.at(i)== 'F')
            {
             output += "1111";
             output2 += "1111";
            }
            output2 += " ";
    }
    
    
    
int temp=32768,ans=0;    
    for(int i = 0; i < 16; i++,temp /= 2)
    {    
    if(output.at(i)-48 == 1)
    ans += temp;             
    }
cout << "The decimal number of FE10 is " << ans <<endl;
cout << "The binary number of FE10 is " << output2 <<endl;
 system("PAUSE");
 return 0;   
}