Input and Output in C++

Streams: cout and cin

C++ handles input and output through streams. cout ("console out") sends data to the screen, and cin ("console in") reads what the user types. Both live in <iostream>.

Output with cout

You send values to cout with the insertion operator <<, and you can chain many together:

int score = 90;
cout << "Your score is " << score << " out of 100\n";

Input with cin

You read a value into a variable with the extraction operator >>:

#include <iostream>
using namespace std;
int main() {
    int age;
    cout << "Enter your age: ";
    cin >> age;
    cout << "Next year you will be " << age + 1 << "\n";
    return 0;
}

Reading multiple values

One cin can read several values in a row — the user separates them with spaces or new lines:

int a, b;
cout << "Enter two numbers: ";
cin >> a >> b;
cout << "Sum = " << a + b << "\n";

Reading a full line

cin >> stops at the first space, so it reads only one word. To read a whole line, including spaces, use getline:

#include <iostream>
using namespace std;
int main() {
    string fullName;
    cout << "Enter your full name: ";
    getline(cin, fullName);
    cout << "Hello, " << fullName << "!\n";
    return 0;
}

Common input pitfalls

• getline after cin >> reads an empty line — clear the buffer first with cin.ignore();.
• Using cin >> name for a full name only captures the first word.
• Typing letters when a number is expected leaves cin in a failed state.
• Mixing up << and >> — output uses <<, input uses >>.

Summary

• C++ input/output uses streams: cout to print, cin to read.
• << sends to output; >> reads into variables.
• One cin can read several values separated by spaces.
• getline(cin, str) reads a full line including spaces.
• Use cin.ignore() to fix an empty getline after reading a number.