Installing Java on a Home machine

1. Installing Java on a Home machine • For Windows Users: Download/Install:Go to • http://www.oracle.com/technetwork/java/javase/downloads/java-archive-downloads-javase7-521261.html Accept License Agreement and then download the file named “jdk-7u25-windows-i586.exe”. Save the file to the desktop and run it. The installer will install Java to:C:\Program Files\Java\jdk1.7.0_25\ Once the installer is finished, you must set your computer's path before Java will work correctly.

2. Installing Java on a Home machine (cont’d) • Setting the Path:Go to the Control Panel and double-click SystemSelect the Advanced tabClick on the Environment Variables buttonLook under System Variables for "Path"Click on "Path" and then click editAdd the following to the end of the Path; C:\Program Files\Java\jdk1.7.0_25\binClick OK.Click the "New" button.For the variable name, type: CLASSPATHFor the value, type: .;NOTE: The above value in words is period semicolon; it is not a misprint.Click OK.Exit out of all the open windows

3. Installing Java on a Home machine (cont’d) • To test if java is installed correctly:Open up a command promptTo do this click on Start and then RunType in cmd.exe and click OkType java and hit enterIf you see something like "command not found", then java is not installed correctlyOtherwise you should see a list ofoptions for running java

4. Developing a programming skill • Learning to program a computer • Training yourself to solve problems • in a very detailed and organized manner • You are already experienced in • Intuitive problem solving • Need to develop programming skill • Write a problem solution • IN terms of actions appropriate for a computer

5. Computer organization • Computer system • Hardware • physical, tangible pieces such as chips, wires, and so on • Useless without instructions to tell them what to do • Driven by a series of instructions, in other words programs • Software • Programs and the data those programs use • Intangible counterpart to the physical hardware components

6. Computer hardware • Most computer have four major hardware parts • Central Processing Unit (CPU): • brain of the computer • executes individual commands of a program • Input/output devices • allow human beings to interact with a computer • Memory • stores programs and data while being processed by CPU

7. Computer hardware (cont’d) Memory Input devices Output devices CPU

8. What is programming • Computers performs tasks • more efficiently, quickly, and accurately • than we could by hand • However, to be useful it must be programmed • Computer programming: • Devise a set of instructions • to be executed by a computer • In order to solve a given real world problem

9. Problem-Solving Phase Implementation Phase Concrete solution (Program) Test Analysis and specification General solution (Algorithm) Verify Maintenance Phase How do we write a program? • It is a two phase process

10. Algorithm implementation JAVA code Peter’s JAVA code Algorithm C++ code Algorithm Nell’s JAVA code Ada code John’s JAVA code Algorithm translated by different people Algorithm translated into different languages

11. Programming shortcut Problem Solving Phase (Algorithm) Problem Shortcut? Implementation Phase (code) Think first and code later

12. JAVA program execution • convert Java code to a form usable by computers • provided that in a computer instructions and data • are stored in the computer memories using binary codes • In a computer, • data represented by pulses of electricity • On circuit => ‘1’; Off circuit => ‘0’ • Data in binary form => combination of enough 1s and 0s • Program execution means • translating data and instructions to patterns of 1s and 0s.

13. Programming language levels • Machine language • Primitive instruction built into each machine • Each type of CPU has its own language • Binary based instructions • => tedious process and prone to error • Assembly language • Short English like words for commands and data • Tedious to use Both are considered to be low level languages

14. Programming language levels (cont’d) • High level language • Expressed in English like phrases • Easier to read and write

15. Program development • Software tools involved • Editor: type a program and store in a file • Translation from high level into executable form • That translation may result in errors • You change the code to fix the problem • Execute the program and evaluate results errors errors Edit and save program Translate program Execute program

16. Compilers • Translation into machine language • Compiler: • Translates code in one language • to equivalent code in another one • Original code => source code, • Target language => particular machine language • Translate once and run whenever needed

17. Interpreters • Translation into machine language • Interpreter • similar to compiler with some differences • Interweaves the translation and execution • Parts of the source code • are translated and executed one at a time • Drawback: • Programs run more slowly, • as translation occurs during execution

18. JAVA translation and execution • The process • combines the use of a compiler and interpreter • Java source code -> Bytecode (Java compiler) • JAVA virtual machine reads bytecode and executes it • Difference between Bytecode and machine language • Bytecode is not tied to any particular processor type • It makes JAVA architecture neutral => portable

19. JAVA translation and execution (cont’d) JAVA Source code JAVA bytecode JAVA compiler JAVA interpreter Bytecode compiler Machine code