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COMPUTER SOFTWARE APPLICATION - CITS

Java is interpreted
Java supports cross-platform code through the Java bytecode. use of Bytecode can be interpreted on any platform
by JVM.
Java is distributed
Java was designed with the distributed environment. Java can be transmit, run over the internet.

JVM, Byte codes and Class path

JDK, JRE, and JVM are essential components in the world of Java programming, each serving a specific role in
the development and execution of Java applications:
JDK (Java Development Kit)
The JDK is a software package provided by Oracle (and other vendors) that includes all the tools and libraries
necessary for Java application development. It contains the following key components:
• Java Compiler (javac): This tool is used to compile Java source code (.java files) into bytecode (.class files),
which can be executed by the Java Virtual Machine (JVM).

• Java Runtime Environment (JRE): The JRE is also included in the JDK. It is needed for running Java
applications but not for developing them. The JRE consists of the JVM and essential libraries.
• Development Tools: The JDK includes various development tools like debugging tools, JavaDoc for generating
documentation, and more.
Developers use the JDK to write, compile, and package Java applications.
JRE (Java Runtime Environment)
The JRE is a subset of the JDK and is required to run Java applications. It includes the following components:

• Java Virtual Machine (JVM): The JVM is the runtime engine responsible for executing Java bytecode.
It interprets and translates bytecode into machine-specific code that the underlying operating system can
understand. Each platform (e.g., Windows, Linux, macOS) has its own JVM implementation,
• Java Standard Library: The JRE includes a set of core libraries and classes that provide essential functionality
to Java applications. These libraries offer features like input/output operations, networking, and more.

End-users who want to run Java applications need the JRE installed on their system. It allows them to execute
Java programs without the need for development tools.
JVM (Java Virtual Machine)

The JVM is the runtime environment in which Java bytecode is executed. It is an integral part of both the JDK and
the JRE. The JVM performs several crucial tasks:
• Loading: It loads compiled Java bytecode (class files) into memory.
• Verification: The JVM checks the bytecode for security and integrity to prevent potential security vulnerabilities.

• Execution: The bytecode is executed by the JVM, which translates it into machine code specific to the
underlying hardware and operating system.
• Memory Management: The JVM manages memory allocation and garbage collection to ensure efficient
memory usage.
• Security: The JVM enforces Java’s security model, including access control, class-loading restrictions, and
more.

JVM Architecture
Java applications are often referred to as WORA, which stands for “Write Once Run Anywhere.” This concept
signifies that a programmer can write Java code on one system and anticipate it to run on any other Java-enabled
system without the need for modifications. This seamless portability is made possible due to the presence of the
Java Virtual Machine (JVM).

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CITS : IT&ITES - Computer Software Application - Lesson 78 - 84

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