Chapter 1: Hello World and Java Concepts (AP Computer Science)

Edit-compile-test loop

A loop executed by a programmer that is made up of 3 main steps that are used to compile & run a program.

Terminal (Console)

A place where you can develop, compile, build, run, and test your code by entering commands into it.

Low-level language

A programming language that is designed to be easy for a computer to execute; also called "machine language" or "assembly language".

High-level language

A programming language that is designed to be easy for humans to read and write. It is compiled into assembly language. For example, Java or Python.

Escape sequence

A sequence of text that creates a special character that can't be created with a string literal in double quotes

Strings

A series of characters stored in memory, for example: names, addresses, greetings such as "Hello World".

operating system

A unique feature of Java is that the executable files are able to run on any ____ ____, which means that it is portable.

Freeform layout

A way of writing code that lets you use as many spaces or line breaks (newlines). Java code has this.

secondary memory

Also known as auxiliary storage: CD-ROM, DVD-ROM, hard drives, thumb drives, cloud storage (servers), solid state drives (SSDs)

IDE

An all-in-one application or program where you can develop, compile, build, run, and test your code.

main

An important function that always has to be declared in a class in Java. This is required for any Java program to run.

System

Class created by Java code (Hello World in main function)

Bus

Connections between the CPU and other parts on the motherboard, has bandwidth

Class files (.class file extension)

Files created when a the compiler compiles a program. It is made up of JVM instructions which do not have human-readable code but is converted into an executable/binary by the JVM.

String[] args

Important parameter inside the main function; the args variable follows the standard Java naming convention.

Data

Information usable by a computer, stored in bits that are either on or off, grouped together into bytes

.class

Java class file extension

applets

Java code that runs in a web browser

.java

Java source code file's extension

System.out.println

Method created by Java code that prints a string and a newline to the console (Hello World in main function)

System.out.print

Method created by Java code that prints a string to the console (Hello World in main function)

Floating point numbers (doubles)

Numbers that have decimal points, displayed in the console as 1.0, not 1

System.out

Object created by Java code (Hello World in main function)

Hardware

Physical equipment

Software

Program that provides functionality

String literal

String enclosed in double quotes "", used when declaring a String variable or printing "Hello World" to the console where "Hello World" is a parameter inside System.out.println()

Syntax error

System.ouch.println("Hello World!")

Logic error

System.out.println("Hello Word!")

Runtime error

System.out.println(12/0)

CPU (central processing unit)

The brain of the computer, executes program instructions including arithmetic operations and low-level code very rapidly

Decimal

When the binary number 11010 is represented as 26, the resulting number is an example of a _______ computer number system.

Binary

When the decimal number 26 is represented as 11010, the resulting number is an example of a _______ computer number system.

Hexadecimal

When the decimal number 26 is represented as 1A, the resulting number is an example of a _______ computer number system.

JVM

Where Java code is compiled and executed in, it uses a number-like syntax for its assembly language.

Case-sensitive

Where uppercase and lowercase letters (variable names, methods, classes, etc) matter. Java specifically has this.

Integers

Whole numbers, positive or negative, no decimal points, displayed in the console as 1, not 1.0

Backslash

\\

Newline

\n

Tab

\t

directory

another name for a folder where files can be stored

whitespace

another name for a tab, a space, or a newline

removable storage

floppy disks, USB flash/thumb drives, tapes, CDs, DVDs

primary memory

random access memory (RAM), read only memory (ROM)

debuggers

software tools that let you find bugs (logic errors) in your programs