Input, Output & Comments

Programs need ways to communicate

Input is information coming into the program. Output is information going out of the program. A comment is a note for people reading the code; the computer ignores it.

A simple program can ask your name, remember the answer, and then greet you.

Ask, save, then show

The steps are more important than the syntax: ask a question, save the answer, then use it.

EXPLANATION Ask the user for a name
ASK "What is your name?" SAVE IN playerName
SHOW "Hello, " + playerName

The same idea in Python

input() asks for text and print() displays output. A # begins a single-line comment.

# Ask the user for a name
playerName = input("What is your name? ")
print("Hello, " + playerName)

The same idea in JavaScript

In a browser, prompt() can collect simple input and console.log() can display output to the developer console.

// Ask the user for a name
const playerName = prompt("What is your name?");
console.log("Hello, " + playerName);

The same idea in C#

Console.ReadLine() reads text typed by the user.

// Ask the user for a name
Console.Write("What is your name? ");
string playerName = Console.ReadLine() ?? "";
Console.WriteLine("Hello, " + playerName);

The same idea in Java

Java commonly uses Scanner for console input.

// Ask the user for a name
Scanner input = new Scanner(System.in);
System.out.print("What is your name? ");
String playerName = input.nextLine();
System.out.println("Hello, " + playerName);

The same idea in C++

std::getline reads a full line of text from standard input.

// Ask the user for a name
std::string playerName;
std::cout << "What is your name? ";
std::getline(std::cin, playerName);
std::cout << "Hello, " << playerName << '\n';