Getting feedback from the user, modifying it, and producing a new
result
Have you ever wondered how online websites take in and verify the
usernames and passwords that you enter? Well, these websites ask the
user for input and process the information that the user sends in,
typically storing this information in variables.
This process used by those programs is called User input, and
it is any information that is sent by the user to a computer using
an input device. In almost every program, user input is utilized in
some form. For example, console applications, desktop applications,
databases, and website pages all use user input.
Below is an example of prompting the user for a password, taking in
the user input, storing the input into a variable, and printing the
password back out.
Code:
password = input("Enter a password: ") # prompting user and reading inputprint("Password is " + password) # outputting user input
Output:
> Enter a password: User types in "Curry30"
> Password is Curry30
Code:
import java.util.Scanner;
publicclassMain{
publicstaticvoidmain(String[] args){
Scanner myObj = new Scanner(System.in); // creating a Scanner object
System.out.println("Enter a password: "); // prompting user
String password = myObj.nextLine(); // reading user input
System.out.println("Password is " + password); // outputting user input
}
}
Output:
> Enter a password: User types in "Lebron23"
> Password is Lebron23
Code:
#include<bits/stdc++.h>usingnamespace std;
intmain(){
cout << "Enter a password: " << endl; // prompting user
string password; cin>>password; // reading user input
cout << "Password is " << password << endl; // outputting user input
}
Output:
> Enter a password:
User types in "Harden13" > Password is Harden13
If you input into the same variable multiple times, only the last
info is kept.
User input works for a variety of data types, including numerical
values. The syntax is different for numerical values, but not
significantly.
Taking in user input and storing it in variables also allows for the
manipulation of input data before producing a final output value. In
other words, calculations could be performed on the input data to
create a different output value, similar to how a function in math
produces an output f(x) from an input x. For example, we could take
in a number x, add 10 to x, and then print out x.
Below is an example of prompting the user for their favorite number,
taking in the user input, multiplying the number by 2, and then
outputting the result.
Note: It is extremely important that the variables you are storing
the inputs in are the correct variables or the ones you want. For
example, if a user inputs 0.55 when a program expects an integer, it
will return an integer(The input is usually rounded to the nearest
one). If a user inputs the string "hello!" when the program expects
an integer, it will fail entirely as the program expects an integer,
and has received something which is not one.
Code:
favNumber = int(input("Enter your favorite number: ")) # prompting user and reading input
favNumber*=2print("Favorite Number X 2 = " + str(favNumber)) # outputting user input
Output:
> Enter your favorite number: User types in "30"
> Favorite Number X 2 = 60
Code:
import java.util.Scanner;
publicclassMain{
publicstaticvoidmain(String[] args){
Scanner myObj = new Scanner(System.in); // creating a Scanner object
System.out.println("Enter your favorite number: "); // prompting userint favNumber = myObj.nextInt(); // reading user input
favNumber*=2;
System.out.println("Favorite Number X 2 = " + favNumber); // outputting user input
}
}
Output:
> Enter your favorite number: User types in "23"
> Favorite Number X 2 = 46
Code:
#include<bits/stdc++.h>usingnamespace std;
intmain(){
cout << "Enter your favorite number: " << endl; // prompting userint favNumber; cin>>favNumber; // reading user input
favNumber*=2;
cout << "Favorite Number X 2 = " << favNumber << endl; // outputting user input
}
Output:
> Enter your favorite number:
User types in “13”
> Favorite Number X 2 = 26
You can play around with all the code we've used in this article on
Replit: