Question

Why does this program run fine?

#include<iostream>
using namespace std;
int main()
{
    cout <<"What year was your house built?\n";
    int year;
    cin >> year;
    cout << "What is its street address?\n";
    char address[80];
    cin>>address;
    cout << "Year built: " << year << endl;
    cout << "Address: " << address << endl;
    cout << "Done!\n";
    return 0;
}

And why does this program not give the chance to enter the address?

#include <iostream>
int main()
{
    using namespace std;
    cout <<"What year was your house built?\n";
    int year;
    cin >> year;
    cout << "What is its street address?\n";
    char address[80];
    cin.getline(address, 80);
    cout << "Year built: " << year << endl;
    cout << "Address: " << address << endl;
    cout << "Done!\n";
    return 0;
}

Answer 1

cin>> leaves the newline character (\n) in the iostream. If getline is used after cin>>, the getline sees this newline character as leading whitespace, thinks it is finished and stops reading any further.

Two ways to solve the problem:

Avoid putting getline after cin >>

OR

Consume the trailing newline character from the cin>> before calling getline, by “grabbing” it and putting it into a “dummy” variable.

string dummy;
getline(cin, dummy);

Why does the first program work & Second doesn’t?

First Program:
The cin statement uses the entered year and leaves the \n in the stream as garbage. The cin statement does NOT read (or “grab”) \n. The cin ignores \n when reading data. So cin in program 1 can read the data properly.

Second Program:
The getline, reads and grabs \n. So, when it sees the \n left out from cin, it grabs the \n and thinks it is finished reading, resulting in second program not working as you expected.