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2.2.2 Java Applet
Applets are Java programs which are downloaded from a website on a client computer and can only be executed
within a web browser. They cannot run independently on a computer like standalone applications. Java Applets
are used for Internet programming, creating animation and games. They are also called Internet Applets.
2.3 JAVA COMPILATION PROCESS
Java is a platform-independent programming language, which means that Java code can run on any platform (such
as Windows, Linux, macOS) without modification. This is achieved through the following steps:
Step 1: The program code is compiled into bytecode through an Operating System independent compiler.
Step 2: This bytecode needs to be converted into machine code to execute on an individual device. This is done by
Java Virtual Machine. The Java Virtual Machine performs all the tasks of the Java runtime system. It loads
the Java class file and interprets the compiled bytecode.
As you know, compiler translates High level language program to a lower-level language to create an executable
program and Interpreter reads the input source program and then translate to machine code instruction by
instruction.
2.3.1 Java Compiler
Java Compiler converts the source code written in Java (with the .java extension) into an intermediate code called
byte code. The Java Compiler is also known as javac.
Java bytecode further is converted by Java Virtual Machine to machine-dependent code.
This bytecode has resemblance with Assembly language. The only difference between Byte code and Assembly
language is that byte code is used by JVM and Assembly language is directly used by the hardware (CPU).
Note: The extension of Java source code is .java and the converted bytecode has the extension .class.
2.3.2 Java Virtual Machine (JVM)
Java Virtual Machine converts Java bytecode to machine code so that it can be executed. Also it can run on any
operating system. It follows the principle of “Write Once, Run Anywhere”. It manages and optimises the program
so that memory usage can be minimised. The Java Programs written by programmers are called Java Source
Code. They are saved with the extension .java. When Java Source Code is compiled by Java Compiler (javac), the
resultant code is called Java bytecode which is further converted by JVM to machine code.
Interpreter
JVM for Mac
Source Code Complier Byte Code Interpreter
(.java file) (Javac) (.class file) JVM for Windows
JVM Interpreter
for Linux
30 Touchpad Computer Applications-IX

