Q) What is loading? And why loading?
·.exe
files, .bin files, .class files are executable files contains machine or jvm
code.
·All
this files are stored in hard disk.
·To
execute all this files by microprocessor these files from hard disk must be
loaded into ram
·To
load .exe files, .bin files the operating system uses static loading.
·In
static loading all executable blocks are loaded into ram if all executable
blocks loading is completed then execution of the program is started
·JVM
loads .class files dynamically, so .class files loading is dynamic loading
·In
dynamic loading 1st main class is loaded, then main function
execution is started
·Based
on main function lines execution if required other classes also loaded
·All
classes in JVM are not loaded at the beginning of main function execution.
·Whenever
main function is under execution at that time remaining classes are loaded
based on requirements.
Environment variables:
PATH: Path
is a environmental variable using which we make JDK and its programs available
to the local operating systems. Path of the JDK has to be mentioned in the
environment variable path.
Using
this environment variable path local operating system would be able to locate
the programs belonging to JDK.
Ex:
path: jdk\bin
CLASSPATH:
CLASSPATH
is also an environment variable using which we make all the library packages
and the required programs available to the JVM. Thus JVM would be locating the
library packages through the environment variables CLASSPATH
Ex:
jdk\lib\tools.jar;jdk\jre\lib\rt.jar
NOTE:
1. Environment
variable path would be used by local operating system and environment variable
class path would be used by JVM.
2. All
the basic library packages which are required for developing a basic java
application are present in “rt.jar” file. In the form of a compressed format.
