1. Programming 2 Intro to Java

2. 1940 1950 1960 1970 1980 1990 2000 Machine code Assembly languages Fortran Basic Pascal Scheme CC++ Java LISP Smalltalk Smalltalk-80 C# Logo The Timeline of Programming Languages

3. Software Development Early era (1950s): Emphasis on efficiency –fast algorithms –small program size –limited memory use Often cryptic code Not user-friendly Emphasis on –programmer’s productivity –team development –reusability of code –easier maintenance –portability Better documented User-friendly Now:

4. Software Development Tools Editor –programmer writes source code Compiler –translates the source into object code (instructions specific to a particular CPU) Linker –converts one or several object modules into an executable program Debugger –stepping through the program “in slow motion,” helps find logical mistakes (“bugs”)

5. IDE — Integrated Development Environment Combines editor, compiler, linker, debugger, other tools Has GUI (graphical user interface) Compiles + links + runs at the click of a button Helps put together a project with several modules (source files)

6. Compiler vs. Interpreter Compiler: checks syntax generates machine- code instructions not needed to run the executable program the executable runs faster Interpreter: checks syntax executes appropriate instructions while interpreting the program statements must remain installed while the program is interpreted the interpreted program is slower Editor Source code Interpreter

7. Java’s Hybrid Approach: Compiler + Interpreter A Java compiler converts Java source code into instructions for the Java Virtual Machine. These instructions, called bytecodes, are the same for any computer / operating system. A Java interpreter executes bytecodes on a particular computer.

8. Why Bytecodes? Platform-independent. Load from the Internet faster than source code. Interpreter is faster and smaller than it would be for Java source. Source code is not revealed to end users. Interpreter performs additional security checks, screens out malicious code.

9. Types of Programs: Console applicationsGUI applications Applets