Java virtual machine

A Java Virtual Machine (JVM) is a process virtual machine that can execute Java bytecode. It is the code execution component of the Java platform. Sun Microsystems has stated that there are over 5.5 billion JVM-enabled devices
       .A Java virtual machine (JVM) interprets compiled Java binary code (called bytecode) for a computer's processor (or "hardware platform") so that it can perform a Java program's instructions.

          In high-level programming languages such as C and C++, we write a program in a human-readable format, and a program called a compiler translates it to a binary format called executable code that the computer can understand and execute. The executable code depends upon the computer machine that we use to execute our program; it is machine dependent. In Java, this process of writing to executing a program is very similar, but with one important difference that allows us to write Java programs that are machine independent.

Using an interpreter, all Java programs are compiled to an intermediate level called byte code. We can run the compiled byte code on any computer with the Java runtime environment installed on it. The runtime environment consists of a virtual machine and its supporting code.

     The Java Virtual Machine is responsible for interpreting Java byte code and translating this into actions or Operating System calls. For example, a request to establish a socket connection to a remote machine will involve an Operating System call. Different Operating Systems handle sockets in different ways - but the programmer doesn't need to worry about such details. It is the responsibility of the JVM to handle these translations so that the Operating System and the CPU architecture on which the Java software is running is completely irrelevant to the developer.

-by SDR