28/12/24
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Q)What is source code ?
   =>Human readable text expressed in any Programming Language
   is nothing but source code.
   Note:- Program code is nothing but the source code.

Q)What is a source file?
=>Text file that contains the source code of a program is nothing but
a source file.

Q)What is compilation in C?
=>C compiler translating the C source code into machine code(binary code)
is nothing but compilation in C.

Q)What is compilation in Java?
=>Java compiler translating the Java source code into byte code
is nothing but compilation in Java.

Q)How to develop and run a Java Application?
Step 1:- write/edit the source code

Step 2:- Save the source code(create the source file).


Step 3:- compile the source code of the source file.

Step 4:-execute the program.

DIAGRAM

Q)Develop a Java application that displays Hello World! on the console. 
class  Hello World{
	public static void main(String[] args) {
		System.out.println("Hello World!");
	}
}
Q)How to compile a Java program?
=>By using "javac" command
      <javac> <source file>
 For eg.
           javac   one.java
Q)What happens in the background when "javac" command is used?

=>"javac" command is given to the Operating System
=>Operating System invokes the compiler.
=>Java compiler does the following things.
       1)It makes a full read of the source code of the source file.
       2)It verifies the syntactical correctness of the source code.
               case i:-  syntactical errors are found
	                Java compiler reports the errors and it doesn't perform   translation.
               case ii:- no syntactical errors are found.
	                =>Java compilers translates the source code into byte code.
			I.e. it generates one or more ".class" files.
Q)How to run/execute a Java program?
=>by using "java" command

       <java> <Initial Class name>
  
    For eg.   java  HelloWorld

Q)Who executes a Java program?
=>JVM

Q)What happens in the background when java command is executed?
=>java command is given to the Operating System.
=>The OS invokes the JVM.
=>JVM does the following things.
    1)JVM loads the specified class file(For eg. HelloWorld.class)
    2)JVM calls the main method and the program's execution starts