Java Virtual Machine commonly known as JVM, which is a software program that takes a Java program and converts it into byte code. The location of the JVM software is above the hardware devices and the operating system. JVM is a part of the Java Runtime Environment (JRE).
What is Java Virtual Machine?
During the installation of JDK, a layer forms over an operating system to run the Java programs. The JVM, which contains a compiler, converts the source code into a byte code (a new “dot class file”). While running, these programs fetch the dot class files from either the local hard disk or external sources like pen drives, external hard disks, etc., or from over a network. Next, the class loader loads these dot class files into the JRE.
Generally, in programming languages such as C, the interpreter or compiler converts the source code into a .exe file. The .exe files enters the actual machine or the microprocessor for program execution. In contrast, the JAVA virtual machine first converts the source code into byte code in a dot class file format. In the second step, the JRE converts the byte code into a microprocessor-specific instruction format before sending it to the microprocessor for execution in Java programming language. For instance, if the microprocessor is 16-bit, the JRE generates a 16-bit code; for a 32-bit processor, it generates a 32-bit code, and so on.
Advantages of Converting the Source Code into Java Byte Code:
The Java virtual machine is responsible for converting the source code into a bytecode, irrespective of the microprocessor’s capacity. In other words, JVM generates byte code for all types of processors. Whether they are 8-bit,16-bit, or 32-bit. Here, to recollect, one byte equals 8-bit. The JVM offers an abstraction environment, which is platform-independent, for the underlying architecture.
Executes the Program in any Operating System/Platform
In C programming language, if the user wishes to run a specific application on another system, there would be some microprocessor-compatible issues. In such a case, the same application cannot run in another system. The user needs to compile the application program once again, making it a tedious process.
On the other hand, Java applications can run in any number of systems without any issues. It is because the JVM takes the responsibility of rectifying the compatibility issues of the microprocessor.
For instance, if the instruction format from another external source is in 16-bit format, but the microprocessor is 32-bit. Then, the JVM converts the 16-bit source code into byte code. Next, the JRE converts the byte code into 32-bit format. The JRE gives zeros to the extra bits, making the code run in that specific microprocessor. Such a process is known as a virtual machine.
Due to such a unique environment, Java programs can execute on any device or operating system that shows compatibility with JVM implementation. As such, Java programming language is famous for the caption, “write once, run anywhere.”
Functions of JVM in Brief
JVM is essential and mainly helps in performing two functions
1) Helps in running Java applications across various operating systems and devices.
2) Management and optimization of program memory.
And the responsibilities of JVM include,
1) Security
2) Garbage Collection
3) Dynamic Memory Allocation
Java Virtual Machine
In the context of a virtual machine, when you compile a Java program, the JAVA virtual machine converts the source code into byte code, also called a dot class file. It’s instruction format is independent of any microprocessor/ OS/platform such type of processing is called a virtual machine.
So, in Java programming language, instead of converting the code to the compatibility of the microprocessor, it is converted to byte code (an eight-bit format). And, between the compiler and the microprocessor, there is a Java runtime environment (JRE), which takes the byte code and converts it into microprocessor compatibility.
What is the Difference between an Actual Machine and a Virtual Machine?
The process of converting the source code into the instruction format, which the microprocessor requires, is known as the actual machine. That’s why structured programming like C is platform-dependent.
The process of converting the source code into binary form, but not converting it into the instruction that is actually required by the microprocessor is known as a virtual machine.
Which Programming Languages are Examples of Actual Machines and Virtual Machines?
In the context of an actual machine, let’s take an example of C programming language, and for a virtual machine, let’s take Java programming.