Input / Output in C++ : Part 3

Taking Input from the Console

Cin

To take input from the user via the console, we use the cin statement.

cin is a predefined variable that reads data from the keyboard with the extraction operator (>>).

Example1:

int x; 
cin >> x; // Get user input from the keyboard 
cout << X;
Input: 5
Output: 5

Example2:

string x; 
cin >> x; // Get user input from the keyboard 
Input1: "Hello" 
Output1: "Hello"

Question: Calculate the Simple Interest.

#include <iostream> 
using namespace std; 
int main() {
    int principal, time;
    double rate, s1;
    cout << "Enter Principal Amount: ";
    cin >> principal;
    cout << "Enter Rate of Interest: ";
    cin >> rate;
    cout << "Enter Time period ";
    cin >> time;
    si = (principal * rate * time) 100;
    cout < "Simple Interest:"<<si;
}
Output:
Enter Principal Amount: 3000
Enter Rate of Interest: 2
Enter Time period: 3
Simple Interest: 180

Question: Add two numbers.

#include <iostream> 
using namespace std; 
int main() { 
    int n1, n2, addition; 
    cout < "Enter two integers: "; 
    cin >> n1 >> n2; 
    addition = n1 + n2; 
    cout << "Sum of the numbers is: " << addition; 
    return 0; 
}
Output: 
Enter two integers: 5 10 
Sum of the numbers is: 15

Getline

• getline() is a standard library function used to read a string or a line from an input stream.

• It is used when inputting strings with spaces between them or processing multiple strings at once.

• The getline() function extracts characters from the input stream and appends them to the string object until the delimiting character is encountered.

• While doing so, the previously stored value in the string object str will be replaced by the input string, if any.

Syntax 1:

istream& getline(istream& is, string& str, char delim);

Parameters:

• is: is an object of the stream class that tells the stream's function the input that needs to be read.

• str: is the string object that stores the input after the stream's reading process is finished.

• delim: defines the delimitation character, which commands the function to stop processing the input. The reading process will stop once the written code reads this command.

Syntax 2:

istream& getline (istream& is, string& str);

The second declaration is almost the same as that of the first one. The only difference is that the latter has a delimitation character by defaulting a new line(\n)character.

Example

#include<iostream>
#include<string>
using namespace std;
int main() {
    string s;
    getline(cin, s);
    cout << s;
    return 0;
}
Input: Hello world
Output: Hello world

Printing to the Console

Cout

The C++ cout is used to produce output on the standard output device, usually the display screen or console. cout is a pre-defined variable that displays some output or text using the insertion operator(<<).

Example:

cout << "Hello World 1"; 
Output: Hello World!

end: It is used to insert a new line character.

Example:

cout << "Hello" << endl; 
cout << "World"; 
Output: 
Hello 
World

To print the variable value, the syntax is as followed

cout << Variable_name;

Example:

#include <iostream> 
using namespace std; 
int main() { 
    int age = 21; 
    string firstName= "King";
    string lastName = "Kong"; 
    cout << "My name is " << firstName << " " << lastName << endl; 
    cout << "My age is " << age << endl; 
    return 0; 
}
Output: 
My name is King Kong 
My age is 21