Programming Process
The programmer performs several steps when writing a computer program. 1. Write the source code for your program. 2. Compile the source code with an appropriate compiler. 3. Execute the compiled, executable program to test it. 4. Debug the program — find the errors and fix them. 5. Repeat the process as needed.
Hello.java is the source code. Source code is a human-readable file written in a programming language. In Java, all of your program code will be placed in a class.
//Source code
public class Hello {
public static void main(String[] args) {
System.out.println("Hello, world");
}
}
The source code is compiled using the program javac.
compiled¶
Translated from your source code statements down to the most elementary level — machine instructions.
The compiled code becomes executable code. This is code that the computer can run. In Java, this is the Hello.class file that the javac program generated. The content of this file is called byte code.
byte code¶
Machine instructions that are executable by any Java Virtual Machine (JVM).
This program can be executed using the java command.
The executable code can use other class files that are known to the compiler. (Don't worry about these files for now.)
Drill¶
simpleprograms/drills
* Open the file Hello.class using any text editor. Note how it is not human-readable. (If you can read it, you probably opened Hello.java.)