Organization of a Computer System

1
Organization of a Computer System
LightsLine PrinterMonitor
Toggle switchesPunch cardsKeyboard
Paper CardVCR Tape Hard disk
2
Are These Computer Systems?

• Laptop
• Cell Phone
• iPod
• TravelMate (gps positioner)?

3
What Is a Program?

• An ordered set of steps that solve a problem is
  called an algorithm.
• A computer program is set of instructions that
  carry out an algorithm.

4
Example of an Algorithm

• Write a algorithm to open a book.
• Thats all Im asking.
• A simple set of instructions to open a book.

5
Algorithm VS Program

• Can a laptop computer execute the algorithm you
  just gave me to open a book?
• To perform a task, the computer requires that the
  algorithm be written in a computer programming
  language.

6
Programming Languages

• Machine
• Assembler
• Basic
• FORTRAN
• COBOL
• Pascal
• PHP

• C
• C
• C
• Java
• Visual Basic

7
How It Works

• The computer can only process instructions that
  are presented as a series of 1s and 0s.
• Machine language is written in zeros and ones
  only!
• Programming languages allow us to use words
  instead of numbers
• Another program (a compiler) converts the
  programming language statements to machine
  language.

8
Algorithm for Computing Gross Pay

• Display message "How many hours did you work?"
• Allow user to enter number of hours worked
• Store the number the user enters in memory
• Display message "How much are you paid per
  hour?"
• Allow the user to enter an hourly pay rate
• Store the number the user enters in memory
• Multiply hours worked by pay rate and store the
  result in memory
• Display a message with the result of the previous
  step

9
Example of a program

• Heres an example of a program written in the PHP
  programming language.
• PHP is used to create interactive Web pages that
  connect to a database.

10
Methods of Programming

• Procedural
• Object Oriented

11
Programming LanguagesCategorized

• Procedural
• Machine
• Assembler
• Basic
• FORTRAN
• COBOL
• Pascal
• PHP
• C

• Object Oriented
• C
• C
• Java
• Visual Basic

12
Methods of Programming Procedural Programming

• What and How? Not relevant to us now.
• 95 of all programs ever written where written
  using the procedural approach.

13
Methods of Programming Object-Oriented

• Everything in the program is considered to be an
  object.
• Objects have attributesYou the programmer set
  the values of the attributes.
• Objects perform tasksYou, the programmer, by
  writing Visual Basic code determine how the
  task will be done.

14
Example of an Object

• This form is an object.
• It has attributes
• Name
• Height
• Width
• Location on screen
• Color

15
Example of an Object

• This form is an object.
• All Visual Basic programs start with a single
  object the form.
• Through programming, we will put additional
  objects on the form and provide tasks for these
  objects to perform.

16
Basic Concepts of OOP

• Object been there, done that.
• Event a task that is triggered when the
  programs USER (not author) provides the
  appropriate input
• Examples of inputs?

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OOP

• Object Oriented Programming then is
• creating objects
• assigning tasks that the objects can do

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OOPSimple Example

• Two Objects (for now)
• Form
• Quit Button
• One Event
• When Quit button is clicked, terminate the
  program