Core Java Notes[(session2)]

1. Execution Process c and cpp program
2. *if we develop any program it has to undergo 2 phases
3. 
   
4. i)compilation
5. ii)execution
6. 
   
7. if we compile a c/cpp program we get an intermediate code called as .obj file.
8. 
   
9. *we execute or convert .obj into .exe using a program called Linker.
10. 
    
11. *.exe is when executed provides output.
12. 
    
13. 
    
14. Here either .obj or .exe of one os cannot be executed on other os,so c/cpp are platform dependent.
15. 
    
16. 
    
17. .c/.cpp-->compile-->.obj-->Linker-->.exe
18. 
    
19. 
    
20. 
    
21. Execution Process of a java program
22. 
    
23. 
    
24. .java--->comiple-->.class[bytecode]--->Jvm-->o/p
25.                                        Jit
26. 
    
27. *we save a java program using the extension .java
28. 
    
29. *Execution of a java program undergoes 2 phases
30. 
    
31. i)compilation
32. ii)execution
33. 
    
34. i)compilation
35. 
    
36. *if we compile a .java program we get .class[bytecode]
37. 
    
38. .java-->compiled-->.class[bytecode]
39. 
    
40. *once we get a .class again we should convert bytecode to machine code using jvm[java virtual machine]
41. 
    
42. *Jvm is a program which helps in converting bc to mc
43. 
    
44. .class-->jvm-->o/p
45. 
    
46. *.class is platform independent code,we can execute the .class file of one os on another os.
47. 
    
48. *.class is interpreted by jvm so jvm is also called as bytecode interpretor.
49. 
    
50. *jvm is platform dependent bcoz every os should have a seperate jvm.
51. 
    
52. what is JIT compiler?
53. 
    
54. It is a helper application of jvm which helps jvm to convert byte code to mahcine code together.
55. 
    
56. 
    
57. .java-->compile-->.class-->jvm-->o/p.