Introduction to Programming

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Introduction to Programming

• Dr. Tim Margush
• University of Akron

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Goals

• Learn about programming a computer
• Understand basic computer architecture
• See the relationship between programming
  languages and architecture
• Become familiar with programming tools
• Compile and execute a Java program

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What is Programming

• Creating a collection of instructions that will
  be followed by a computing device
• What instructions does it understand?
• How are the instructions recorded?
• What are the rules for ordering the instructions?
• How does the computer know what instructions it
  is to execute?

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Basic Computer Architecture
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VonNeumann Architecture

• Program instructions and data are numerically
  encoded and stored in RAM
• The CPU fetches and executes instructions
• Default execution order is sequence
• Instructions can interrupt the sequential
  processing to begin a fetch sequence from an
  arbitrary location

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Fetch-Execute Cycle

• IP Instruction pointer
• Address of next instruction to be fetched
• Fetch instruction at IP
• Increment IP (anticipate sequence)
• Decode and execute instruction

See it in action compliments of Richard
Jones http//www.ib-computing.com/oldIB/FE_cycle.h
tm
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Programming Languages

• Machine language
• Numeric 04 A2 C9 FF 29
• Assembly language
• Mnemonic, symbolic LOAD R13,AGE
• Assembled to machine language
• High-level language
• Expressive and symbolic, almost natural(?)
  discount price .25
• Compiled to machine language

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Steps to Run a Program

• Edit, Compile, Load, Execute
• The sequence below illustrates the process in the
  context of the Java programming language

notepad Sample.java
java Sample
javac Sample.java
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Java

• Simple, familiar (C-like), object-oriented,
  robust, secure, architecture-neutral,
  interpreted, dynamic, multi-threaded,
  high-performance
• Programs are compiled to a standard intermediate
  format (class file)
• Class files are interpreted by a Java Virtual
  Machine (JVM) specific to each host environment

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Programming Tools

• Editor
• Any text editor will suffice (notepad)
• A Java-aware editor will provide formatting and
  shortcuts, and suggestions appropriate to the
  language (jEdit)
• An integrated development environment (IDE) will
  automatically connect the editor with project
  management and compilation, execution, and
  debugging tools (jGRASP or Eclipse)

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Programming Tools (2)

• Compiler
• SUN provides free and commercial compilers
• Sun Java J2SE (Java version 2, standard edition)
• Other vendors bundle compilers with their IDE
• Borland Jbuilder
• Symantec VisualCafe
• IBM WebSphere Studio
• Metrowerks CodeWarrior

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Programming Tools (3)

• Java Virtual Machine
• SUN (included with SDK)
• Microsoft (often included with IE installations)
• Others? (students sometimes write their own)
• Sometimes called a Java Runtime Environment (JRE)
• Specific to each platform (hardware/OS)
• Required to run Java programs

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jGRASP

• Free IDE that uses Suns Java SDK
• Download from http//www.jgrasp.org

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Eclipse

• Open Source IDE that uses Suns Java SDK
• Download from http//www.eclipse.org

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Java Programs

• Source code
• Stored in a file with .java extension
• Usually placed in a folder that holds all of the
  files related to one program
• Class file
• The compiled version of a source file
• Usually located in the same folder as the source

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A Simple Java Program
Class name
Method name

• public class MyName
• public static void main(String args)
• //display my name
• System.out.println("My name is Harold.")

Method parameters
Program comment
String argument
Method call
System output object
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Compiling the Program (jGRASP)
Compile button
Source code
Compile messages
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Running the Program (jGRASP)
Run button
Class file from compile
Program output
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Compiling the Program (Eclipse)
Compile button
Source code
Compile messages
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Running the Program (Eclipse)
Run button
Program output
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Summary

• Programs are instructions that will be followed
  by a central processing unit (CPU) in the context
  of a computing system
• Data and program instructions are in RAM during
  program execution
• Programs are written in machine, assembly, or a
  high-level language
• High-level languages (such as Java) are compiled
  before they can be run

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Summary (2)

• The steps to running a program are edit,
  compile, load (link and run)
• Java programs are executed in a virtual machine
  (JVM) that is the standardized across all
  computing platforms
• Java programs are collections of classes
• Classes contain methods (actions)
• When a class file is run as an application, the
  JVM follows the instructions in the method named
  main