Principles of Programming

From Lesson 1-1: In HelloWorld.java, replace this line of code ... // TODO code application logic here ... with this: System.out.println("Hello World!"); Now, head over to the Run menu, and select "Run Project". The program should output the following text: Hello World! To output, or print something is to write it on the screen. The output is the text that gets written on the screen. Congratulations! You have just written your first Java program! Traditionally, when you learn a new programming language, the first program you write is one that prints Hello World! on the screen. In the next lesson, you will learn about the different parts of this program. From Lesson 4-2: A variable is used to store a value. However, a variable IS NOT THE SAME THING AS its value! The variable here is score, and its value is 1400. A value is meaningful in the context of a program. For example, 1400, in a game, could be a player's score, while 1400, in an encyclopedia program, could be a year in history. The = (assignment) operator tells Java to assign the value, 1400, to the variable, score. In an assignment statement, the variable ALWAYS goes on the left side of the =, and the value ALWAYS goes on the right side of the =. Picture the = operator as an arrow pointing to the left (←): int score ← 1400; Think of it, and say it as, "int score gets 1400." From Lesson 5-2: In "arrow form", step-by-step: int counter ← 0; counter ← counter + 1; counter ← 0 + 1; counter ← 1; Therefore, after the second assignment statement is executed, the value of counter is 1. Assignment statements, like the second one, are VERY common! For example, in a game, if a player scores 100 points, an assignment statement, like score = score + 100;, exists somewhere in the game's code, and gets executed, in order to update the player's score. From Lesson 7-1: It's impractical to change the code, and re-compile it, every time the program needs to be run with different data. Thankfully, a program can receive data from its user (person who uses a computer or program). This can be done, using Java's built-in Scanner class. From Lesson 8-1: You may think your computer is "smart". You may even own a "smart phone". However, computers actually have no intelligence at all! A computer can only do what it has been programmed to do. It gets its apparent "intelligence" from the cleverness of its programmers. Computers are actually pretty stupid! They have to be told EXACTLY how to do everything, step by step. They do not have the instincts or intuition that animals and humans have. They do not think, although they do decide, in a sense. The "thought process" of a computer is quite simplistic: everything is either on or off, yes or no, black or white, one or zero, true or false. A computer runs on electricity. Think of its electrical circuits as containing many tiny light bulbs, which can either be on or off, depending on how various light switches are flipped. From the Master Vocabulary List: software development – Software development is the process of creating, testing, and improving upon software. See software. token – A token is a string that can be treated as a "whole piece" of data, rather than as a sequence of individual characters. For example, in ordinary speech and writing, words are tokens. A word, like "box", is very different from the letters, "b", "o", and "x", by themselves. See data, string.